DHS COMPARATIVE 

REPORTS 23

FERTILITY TRANSITION IN 

SUB-SAHARAN AFRICA: 

A COMPARATIVE ANALYSIS OF 

COHORT TRENDS IN 30 COUNTRIES

APRIL 2009

This publication was produced for review by the United States Agency for International Development (USAID). It was prepared by 

Stacy E. Sneeringer of Wellesley College.

FERTILITY TRANSITION IN SUB-SAHARAN AFRICA: 

A COMPARATIVE ANALYSIS OF COHORT TRENDS IN 30 COUNTRIES DHS COMPARATIVE REPORTS 23
MEASURE DHS assists countries worldwide in the collection and use of data to monitor and 

evaluate population, health, and nutrition programs. Additional information about the 

MEASURE DHS project can be obtained by contacting Demographic and Health Research 

Division, ICF Macro, 11785 Beltsville Drive, Suite 300, Calverton, MD 20705 (telephone: 301-

572-0200; fax: 301-572-0999; e-mail: reports@macrointernational.com; internet: 

www.measuredhs.com). 

The main objectives of the MEASURE DHS project are: 

to provide decisionmakers in survey countries with information useful for informed 

policy choices; 

to expand the international population and health database; 

to advance survey methodology; and 

to develop in participating countries the skills and resources necessary to conduct highquality demographic and health surveys. 
DHS Comparative Reports No. 23 

Fertility Transition in Sub-Saharan Africa: 

A Comparative Analysis of Cohort Trends in 

30 Countries 

Stacy E. Sneeringer 

ICF Macro 

Calverton, Maryland, USA

April 2009 

Address for correspondence: Stacy E. Sneeringer, Department of Economics, Wellesley College, 106 

Central St., Wellesley, MA 02481; Phone: 781-283-2989; Email: ssneerin@wellesley.edu.
Editor: Bryant Robey 

Document Production: Yuan Gu 

This study was carried out with support provided by the United States Agency for International 

Development (USAID) through the MEASURE DHS project (#GPO-C-00-03-00002-00). The 

views expressed are those of the authors and do not necessarily reflect the views of USAID or 

the United States Government. 

Recommended citation: 

Sneeringer, Stacy E. 2009. Fertility Transition in Sub-Saharan Africa: A Comparative Analysis 

of Cohort Trends in 30 Countries. DHS Comparative Reports No. 23. Calverton, Maryland, 

USA: ICF Macro. 
iii 

Contents 

Tables and Appendix Tables v 

Figures and Appendix Figures ix 

Preface xi 

Acknowledgements xiii 

Executive Summary xv 

1 Introduction 1 

1.1 Measuring Fertility 2 

2 Data and Methods 5 

2.1 Data 5 

2.2 Panel Creation 7 

2.3 Data Limitations 10 

3 Fertility Trends by Mother’s Birth Cohort 11 

3.1 Cumulative Number of Births by Mother’s Birth Cohort 11 

3.2 Age-Specific Fertility Rates by Mother’s Birth Cohort 12 

4 Discussion and Conclusions 21 

References 23 

Appendix A Construction of Sample Weights 25 

 A.1 Weights for Analyses of Individual Countries 25 

A.2 Weights for Relative Population Size by Age Group, Country, and Year 27 

A.3 Impact of Weights in Calculation of Statistics 29 

 A.3.1 Weighting Age-Specific Fertility Rates 29 

A.3.2 Weighting Cumulative Number of Births by Age Group 30 

A.3.3 Calculating t-Statistic for Differences between ASFRs by Cohort 31 

 

Appendix B Figures and Tables for Individual Countries 33 

Appendix C Cohort/Age Group Statistics Suppressed Due to Small Sample Size 125 

 

v 

Tables 

Table 2.1 Sample sizes of DHS fertility data used, by country and survey year 6 

Table 2.2 Example of panel creation 8 

Table 2.3 Years Covered by DHS Surveys and by Panel 9 

Table 3.1 23 Sub-Saharan African countries: Age-specific fertility rates by mother's 

age group and birth cohort 14 

Table 3.2 23 Sub-Saharan African countries: Differences in age-specific fertility rates 

between mothers' birth cohorts 16 

Table 3.3 Percentage difference between cohorts in average age-specific fertility rates 

 for ages 15-29 18 

Table 3.4 Percentage difference between cohorts born between 1940 and 1979 in 

 age-specific fertility rates 19 

Appendix Tables 

Table A.1 Example of weighting scheme in individual country analyses 27 

Table B.1.1 Benin: Age-specific fertility rates by mother's age group and birth cohort 35 

Table B.1.2 Benin: Differences in age-specific fertility rates between mothers' birth 

 cohorts 36 

Table B.2.1 Burkina Faso: Age-specific fertility rates by mother's age group and birth 

 cohort 38 

Table B.2.2 Burkina Faso: Differences in age-specific fertility rates between mothers' 

 birth cohorts 39 

Table B.3.1 Burundi: Age-specific fertility rates by mother's age group and birth cohort 41 

Table B.3.2 Burundi: Differences in age-specific fertility rates between mothers' birth 

 cohorts 42 

Table B.4.1 Cameroon: Age-specific fertility rates by mother's age group and birth cohort 44 

Table B.4.2 Cameroon: Differences in age-specific fertility rates between mothers' birth 

cohorts 45 

Table B.5.1 Central African Republic: Age-specific fertility rates by mother's age group 

and birth cohort 47 

Table B.5.2 Central African Republic: Differences in age-specific fertility rates between 

mothers' birth cohorts 48 

Table B.6.1 Chad: Age-specific fertility rates by mother's age group and birth cohort 50 

Table B.6.2 Chad: Differences in age-specific fertility rates between mothers' birth 

 cohorts 51 

Table B.7.1 Comoros: Age-specific fertility rates by mother's age group and birth cohort 53 

Table B.7.2 Comoros: Differences in age-specific fertility rates between mothers' birth 

 cohorts 54 

Table B.8.1 Congo: Age-specific fertility rates by mother's age group and birth cohort 56 

Table B.8.2 Congo: Differences in age-specific fertility rates between mothers' birth 

 cohorts 57 

Table B.9.1 Côte d’Ivoire: Age-specific fertility rates by mother's age group and birth 

 cohort 59 

Table B.9.2 Côte d’Ivoire: Differences in age-specific fertility rates between mothers' 

 birth cohorts 60 

Table B.10.1 Gabon: Age-specific fertility rates by mother's age group and birth cohort 62 
vi 

Table B.10.2 Gabon: Differences in age-specific fertility rates between mothers' birth 

 cohorts 63 

Table B.11.1 Ghana: Age-specific fertility rates by mother's age group and birth cohort 65 

Table B.11.2 Ghana: Differences in age-specific fertility rates between mothers' birth 

 cohorts 66 

Table B.12.1 Guinea: Age-specific fertility rates by mother's age group and birth cohort 68 

Table B.12.2 Guinea: Differences in age-specific fertility rates between mothers' birth 

 cohorts 69 

Table B.13.1 Kenya: Age-specific fertility rates by mother's age group and birth cohort 71 

Table B.13.2 Kenya: Differences in age-specific fertility rates between mothers' birth 

 cohorts 72 

Table B.14.1 Lesotho: Age-specific fertility rates by mother's age group and birth cohort 74 

Table B.14.2 Lesotho: Differences in age-specific fertility rates between mothers' birth 

 cohorts 75 

Table B.15.1 Liberia: Age-specific fertility rates by mother's age group and birth cohort 77 

Table B.15.2 Liberia: Differences in age-specific fertility rates between mothers' birth 

 cohorts 78 

Table B.16.1 Madagascar: Age-specific fertility rates by mother's age group and birth 

 cohort 80 

Table B.16.2 Madagascar: Differences in age-specific fertility rates between mothers' 

 birth cohorts 81 

Table B.17.1 Malawi: Age-specific fertility rates by mother's age group and birth cohort 83 

Table B.17.2 Malawi: Differences in age-specific fertility rates between mothers' birth 

 cohorts 84 

Table B.18.1 Mali: Age-specific fertility rates by mother's age group and birth cohort 86 

Table B.18.2 Mali: Differences in age-specific fertility rates between mothers' birth 

 cohorts 87 

Table B.19.1 Mozambique: Age-specific fertility rates by mother's age group and birth 

 cohort 89 

Table B.19.2 Mozambique: Differences in age-specific fertility rates between mothers' 

 birth cohorts 90 

Table B.20.1 Namibia: Age-specific fertility rates by mother's age group and birth cohort 92 

Table B.20.2 Namibia: Differences in age-specific fertility rates between mothers' birth 

 cohorts 93 

Table B.21.1 Niger: Age-specific fertility rates by mother's age group and birth cohort 95 

Table B.21.2 Niger: Differences in age-specific fertility rates between mothers' birth 

 cohorts 96 

Table B.22.1 Nigeria: Age-specific fertility rates by mother's age group and birth cohort 98 

Table B.22.2 Nigeria: Differences in age-specific fertility rates between mothers' birth 

 cohorts 99 

Table B.23.1 Rwanda: Age-specific fertility rates by mother's age group and birth cohort 101 

Table B.23.2 Rwanda: Differences in age-specific fertility rates between mothers' birth 

 cohorts 102 

Table B.24.1 Senegal: Age-specific fertility rates by mother's age group and birth cohort 104 

Table B.24.2 Senegal: Differences in age-specific fertility rates between mothers' birth 

 cohorts 105 

Table B.25.1 South Africa: Age-specific fertility rates by mother's age group and birth 

 cohort 107 

Table B.25.2 South Africa: Differences in age-specific fertility rates between mothers' 

 birth cohorts 108 

Table B.26.1 Tanzania: Age-specific fertility rates by mother's age group and birth cohort 110 
vii 

Table B.26.2 Tanzania: Differences in age-specific fertility rates between mothers' birth 

 cohorts 111 

Table B.27.1 Togo: Age-specific fertility rates by mother's age group and birth cohort 113 

Table B.27.2 Togo: Differences in age-specific fertility rates between mothers' birth 

 cohorts 114 

Table B.28.1 Uganda: Age-specific fertility rates by mother's age group and birth cohort 116 

Table B.28.2 Uganda: Differences in age-specific fertility rates between mothers' birth 

 cohorts 117 

Table B.29.1 Zambia: Age-specific fertility rates by mother's age group and birth cohort 119 

Table B.29.2 Zambia: Differences in age-specific fertility rates between mothers' birth 

 cohorts 120 

Table B.30.1 Zimbabwe: Age-specific fertility rates by mother's age group and birth 

 cohort 122 

Table B.30.2 Zimbabwe: Differences in age-specific fertility rates between mothers' birth 

 cohorts 123 

Table C.1 Values suppressed due to sample sizes under 250 125 

ix 

Figures

Figure 3.1 23 Sub-Saharan African countries: Cumulative number of births, by 

mother’s age and birth cohort 12 

Figure 3.2 23 Sub-Saharan African countries: Age-specific fertility rates, by mother’s

year of birth 13 

Appendix Figures 

Figure B.1.1 Benin: Cumulative number of births, by mother’s age and birth cohort 34 

Figure B.1.2 Benin: Age-specific fertility rates, by mother’s birth cohort 34 

Figure B.2.1 Burkina Faso: Cumulative number of births, by mother’s age and birth

 cohort 37 

Figure B.2.2 Burkina Faso: Age-specific fertility rates, by mother’s birth cohort 37 

Figure B.3.1 Burundi: Cumulative number of births, by mother’s age and birth cohort 40 

Figure B.3.2 Burundi: Age-specific fertility rates, by mother’s birth cohort 40 

Figure B.4.1 Cameroon: Cumulative number of births, by mother’s age and birth cohort 43 

Figure B.4.2 Cameroon: Age-specific fertility rates, by mother’s birth cohort 43 

Figure B.5.1 Central African Republic: Cumulative number of births, by mother’s age 

and birth cohort 46 

Figure B.5.2 Central African Republic: Age-specific fertility rates, by mother’s birth

cohort 46 

Figure B.6.1 Chad: Cumulative number of births, by mother’s age and birth cohort 49 

Figure B.6.2 Chad: Age-specific fertility rates, by mother’s birth cohort 49 

Figure B.7.1 Comoros: Cumulative number of births, by mother’s age and birth cohort 52 

Figure B.7.2 Comoros: Age-specific fertility rates, by mother’s birth cohort 52 

Figure B.8.1 Congo: Cumulative number of births, by mother’s age and birth cohort 55 

Figure B.8.2 Congo: Age-specific fertility rates, by mother’s birth cohort 55 

Figure B.9.1 Côte d’Ivoire: Cumulative number of births, by mother’s age and birth cohort 58 

Figure B.9.2 Côte d’Ivoire: Age-specific fertility rates, by mother’s birth cohort 58 

Figure B.10.1 Gabon: Cumulative number of births, by mother’s age and birth cohort 61 

Figure B.10.2 Gabon: Age-specific fertility rates, by mother’s birth cohort 61 

Figure B.11.1 Ghana: Cumulative number of births, by mother’s age and birth cohort 64 

Figure B.11.2 Ghana: Age-specific fertility rates, by mother’s birth cohort 64 

Figure B.12.1 Guinea: Cumulative number of births, by mother’s age and birth cohort 67 

Figure B.12.2 Guinea: Age-specific fertility rates, by mother’s birth cohort 67 

Figure B.13.1 Kenya: Cumulative number of births, by mother’s age and birth cohort 70 

Figure B.13.2 Kenya: Age-specific fertility rates, by mother’s birth cohort 70 

Figure B.14.1 Lesotho: Cumulative number of births, by mother’s age and birth cohort 73 

Figure B.14.2 Lesotho: Age-specific fertility rates, by mother’s birth cohort 73 

Figure B.15.1 Liberia: Cumulative number of births, by mother’s age and birth cohort 76 

Figure B.15.2 Liberia: Age-specific fertility rates, by mother’s birth cohort 76 

Figure B.16.1 Madagascar: Cumulative number of births, by mother’s age and birth cohort 79 

Figure B.16.2 Madagascar: Age-specific fertility rates, by mother’s birth cohort 79 

Figure B.17.1 Malawi: Cumulative number of births, by mother’s age and birth cohort 82 

Figure B.17.2 Malawi: Age-specific fertility rates, by mother’s birth cohort 82 

Figure B.18.1 Mali: Cumulative number of births, by mother’s age and birth cohort 85 

Figure B.18.2 Mali: Age-specific fertility rates, by mother’s birth cohort 85 

Figure B.19.1 Mozambique: Cumulative number of births, by mother’s age and birth cohort 88 
x 

Figure B.19.2 Mozambique: Age-specific fertility rates, by mother’s birth cohort 88 

Figure B.20.1 Namibia: Cumulative number of births, by mother’s age and birth cohort 91 

Figure B.20.2 Namibia: Age-specific fertility rates, by mother’s birth cohort 91 

Figure B.21.1 Niger: Cumulative number of births, by mother’s age and birth cohort 94 

Figure B.21.2 Niger: Age-specific fertility rates, by mother’s birth cohort 94 

Figure B.22.1 Nigeria: Cumulative number of births, by mother’s age and birth cohort 97 

Figure B.22.2 Nigeria: Age-specific fertility rates, by mother’s birth cohort 97 

Figure B.23.1 Rwanda: Cumulative number of births, by mother’s age and birth cohort 100 

Figure B.23.2 Rwanda: Age-specific fertility rates, by mother’s birth cohort 100 

Figure B.24.1 Senegal: Cumulative number of births, by mother’s age and birth cohort 103 

Figure B.24.2 Senegal: Age-specific fertility rates, by mother’s birth cohort 103 

Figure B.25.1 South Africa: Cumulative number of births, by mother’s age and birth

 cohort 106 

Figure B.25.2 South Africa: Age-specific fertility rates, by mother’s birth cohort 106 

Figure B.26.1 Tanzania: Cumulative number of births, by mother’s age and birth cohort 109 

Figure B.26.2 Tanzania: Age-specific fertility rates, by mother’s birth cohort 109 

Figure B.27.1 Togo: Cumulative number of births, by mother’s age and birth cohort 112 

Figure B.27.2 Togo: Age-specific fertility rates, by mother’s birth cohort 112 

Figure B.28.1 Uganda: Cumulative number of births, by mother’s age and birth cohort 115 

Figure B.28.2 Uganda: Age-specific fertility rates, by mother’s birth cohort 115 

Figure B.29.1 Zambia: Cumulative number of births, by mother’s age and birth cohort 118 

Figure B.29.2 Zambia: Age-specific fertility rates, by mother’s birth cohort 118 

Figure B.30.1 Zimbabwe: Cumulative number of births, by mother’s age and birth cohort 121 

Figure B.30.2 Zimbabwe: Age-specific fertility rates, by mother’s birth cohort 121 
xi 

Preface

One of the most significant contributions of the MEASURE DHS program is the creation of an 

internationally comparable body of data on the demographic and health characteristics of populations in 

developing countries. The DHS Comparative Reports series examines these data across countries in a 

comparative framework. The DHS Analytical Studies series focuses on specific topics. The principal 

objectives of both series are to provide information for policy formulation at the international level and to 

examine individual country results in an international context. Whereas Comparative Reports are 

primarily descriptive, Analytical Studies have a more analytical approach. 

The Comparative Reports series covers a variable number of countries, depending on the availability of data sets. Where possible, data from previous DHS surveys are used to evaluate trends over 

time. Each report provides detailed tables and graphs organized by region. Survey-related issues such as 

questionnaire comparability, survey procedures, data quality, and methodological approaches are addressed as needed. 

The topics covered in Comparative Reports are selected by MEASURE DHS staff in conjunction 

with the U.S. Agency for International Development. Some reports are updates of previously published 

reports. 

It is anticipated that the availability of comparable information for a large number of developing 

countries will enhance the understanding of important issues in the fields of international population and 

health by analysts and policymakers. 

Ann Way 

Project Director 

xiii 

Acknowledgments 

The author would like to thank Virginia C. Ritter, Lehui Liang, and Jing Chen for valuable 

research assistance. The author would also like to thank Sarah Bradley, Vinod Mishra, Rand 

Stoneburner, and two anonymous reviewers for helpful guidance and comments. 

xv 

Executive Summary 

This study examines fertility trends for 30 sub-Saharan African countries with Demographic and 

Health Surveys (DHS) between 1986 and 2006. The study uses women’s birth histories to construct 

panel data that enable calculation of fertility by mother’s birth cohort. The panel comprises women born 

between 1937 and 1990 and covers their fertility behavior between 1952 and 2005. The study’s focus on 

cohort trends in fertility distinguishes it from many other studies of fertility transition and enables 

examination of women’s fertility over their own lifetimes, rather than what fertility rates at a single point 

in time. 

Over the past five decades, most countries studied show signs of fertility decline in the cohort 

measures examined. Comparing women born between 1950 and 1959 with those born between 1960 and 

1969 reveals that 17 of the 30 countries studied show rates of fertility decline indicative of fertility 

transition. However, there is significant variation among countries in fertility levels and trends. 

This study also finds some “stalling” in fertility declines in a few countries, as decreases in 

fertility become less pronounced than in the past. Fertility decline stalling for most age groups can be 

witnessed in the Congo (Brazzaville) and Madagascar. In several other countries, stalling is only 

witnessed in certain age groups, while in some countries fertility is increasing among certain age groups. 

Thus these data contain suggestions of stalling fertility transitions. For nearly all countries, however, 

cohort fertility rates for women born in the most recent past show decreases suggesting little evidence of 

an unequivocal reversal in Africa’s fertility transition. 

The largest percentage fertility declines by age group appear for women aged 15-19. This pattern 

suggests that women are delaying the start of reproduction. Beyond this youngest reproductive age 

group, fertility declines are similar for younger and older age groups for most countries in the study. 

There is some evidence that earlier cohorts have larger fertility declines among older women, followed by 

declines among younger women in subsequent cohorts. 

The analysis offered here is intended to provide a starting point for further analysis of the 

retrospective cohort fertility data detailed in this report. Retrospective data may suffer from bias related 

to recall errors or sample selection. The extent of bias related to retrospective data is unknown and could 

be a factor in the trends represented here. The large number of data tables and figures included in this 

report (see Appendix B for data tables and figures for each country studied) present new opportunities for 

exploring fertility trends in sub-Saharan Africa and are included for this purpose. 

1 

1 Introduction 

This report provides a comparative analysis of fertility trends in 30 sub-Saharan African 

countries, using data from 74 Demographic and Health Surveys (DHS) conducted between 1986 and 

2006. Unlike much work on fertility trends, in this report I examine fertility by mother’s birth cohort. 

The goal is to examine four main questions: First, what countries are experiencing fertility declines, and 

at what rates? Second, can the reported stalls in fertility decline be found in cohort measures? Third, 

between what cohorts is fertility decline largest? Fourth, among what age groups is fertility declining the 

most? 

The point of this study is not to suggest causal mechanisms of changes or differences (or lack 

thereof) in fertility rates. Rather, this study provides a description of fertility trends by mother’s birth 

cohort in order to discern fertility patterns over the past five decades. The goal is to examine overall 

trends and to compare countries in these trends. 

 While period measures of fertility, such as the period total fertility rate (TFR) and age-specific 

fertility rates (ASFRs), are more readily calculated than the cohort measures used in this report, they can 

sometimes be misleading predictors of future fertility. This would be the case if cohorts are changing 

their fertility patterns by age.1

 However, following birth cohorts over time to examine their fertility 

behaviors is difficult, and total fertility over all reproductive years can only be calculated at the end of 

those years. 

In order to understand how women born at different periods in time may alter their fertility 

patterns, I construct a panel using the fertility histories of survey respondents. The coverage of fertility 

in the panel differs by country based on date and number of DHS surveys, but allows more comparisons 

across countries and years. The panel shows women born between 1937 and 1990, and covers the years 

between 1952 (in the earliest case) and 2005 (in the latest). 

 The study is divided into sections examining different types of fertility measures. Section 2, 

“Data and Methods,” describes the data, panel creation, and variables used in this study. Section 3, 

“Fertility Trends by Mother’s Birth Cohort,” examines cohort measures of fertility, including cumulative 

births by cohort and age-specific fertility by cohort. Section 4 provides conclusions. In all sections, I 

focus entirely on cohort measures, to add a dimension to the literature that more commonly examines 

period rates. 

 I present results for the grouped countries in the main body of the report. There is much to 

suggest that countries in sub-Saharan Africa may be similar in their demographic behavior (see Cleland, 

Onuoha, and Temaeus, 1994, for a discussion). However, the grouped analysis masks substantial 

variation across countries. The report therefore includes an extended appendix containing all measures for 

individual countries (Appendix B). 

In constructing a panel using fertility histories, I attempt to examine measures that one can 

witness for multiple, continuous years. While many countries have multiple DHS surveys that can be 

used to examine trends, these analyses are based on only a few points in time, reflecting the various DHS 

survey periods. 

DHS data contain a great number of variables. However, most of them only cover information on 

the respondent at the time of the interview. For example, the DHS asks the educational status of the 

 

1

 For a discussion of problems arising between period versus cohort fertility measures, see for example Bongaarts 

(2002). 
2 

respondent at the time of the survey, but the survey does not reveal for how long the respondent has had 

this educational status. Thus one cannot construct cohort measures of fertility by these “static” categories 

unless one assumes that people never change categories. For example, I cannot construct completed 

fertility by educational status without assuming that respondents have never changed educational level 

throughout their reproductive lives. I avoid making this type of assumption here and therefore avoid 

analyses that rely on variables that can only be determined for each respondent at the time of the 

interview. 

1.1 Measuring Fertility 

 A number of measures can be used to describe a country’s fertility levels and trends. One of the 

most common is the total fertility rate which represents the number of births a woman is expected to have 

over the course of her reproductive years. The TFR can be defined in period or cohort terms. While most 

research uses period measures, the main contribution of this report is its focus on cohort measures. This 

section outlines the differences between period versus cohort measures. 

The period TFR is constructed using data from a single year by summing period age-specific 

fertility rates. A period ASFR is defined as the number of births to women of a specific age during the 

period, divided by the number of women-years spent at that specific age during the period.2

 In order to 

calculate the period TFR, the period age-specific fertility rates are summed. The resulting total provides a 

representation of how many children a woman is expected to have in the course of her childbearing years 

(normally defined as age 15-49). If one wants to avoid extrapolating period ASFRs, then all ages 

between 15 and 49 must be covered by the sample to construct a period TFR. A DHS samples women 

age 15- 49 at a single point; therefore the period TFR constructed from DHS data will only represent that 

point in time, unless further data are extrapolated. 

Notably, the period TFR is based on a synthetic cohort—which assumes that a woman will follow 

the age-specific fertility rates for that period throughout her childbearing years. While the period TFR 

provides an indication of expected fertility trends, it can result in inaccurate predictions, particularly if 

fertility patterns change between cohorts. A primary instance of when period and cohort TFR may differ 

is the “tempo effect.” In demography, the word “tempo” denotes timing of births. 

To illustrate how the tempo effect can cause disparities between the period and cohort TFRs, 

consider this example. Suppose Woman A is born in 1950, while Woman B is born in 1960. If we 

examine data for 1985, we might find that Woman A had three births at age 25, while Woman B had only 

two births by this age. Thus we might suspect that fertility rates are declining. However, if we examine 

data for both women at age 49, the end of their reproductive years, we might find that each had six births. 

This result would only be possible if Woman B “caught up” when she was between ages 25 and 49. If 

indicative of the general fertility trends, it would suggest a tempo effect— that women born in 1960 

delayed fertility before age 25 but caught up later. 

The tempo effect can work in the opposite direction, too, if for example women born in 1960 

have shorter intervals between births, or begin childbearing earlier than women born in 1950. Women 

born in 1960 may end their reproductive years with the same number of births as women born in 1950, 

but have had more births at younger ages. 

To avoid these possible tempo effects, it is sometimes advisable to examine cohort TFR, or 

completed fertility, rather than to rely on the period TFR based on period ASFRs. A cohort TFR can only 

 

2

 ASFRs are frequently multiplied by 1,000 so that they represent births per 1,000 women of that age. We do not 

multiply by 1,000 when we construct our ASFRs, so they are read as births per woman of that age group. 
3 

be calculated once women born in a certain time period complete their childbearing years. In the 

example, the cohort TFR of women born in 1950 could not be calculated until 1999, when these women 

reached age 49, the end of their childbearing years. Because of this time lag, however, the period TFR is 

a much more frequently used measure than cohort TFR. 

5 

2 Data and Methods

2.1 Data 

In this study I use individual-level data from 74 DHS conducted in 30 sub-Saharan African 

countries between 1986 and 2006. I focus on the female samples, including data on women age 15-49. 

Table 2.1 lists all countries and years included, as well as sample sizes. For each country survey, the data 

include mother’s date of birth, the interview date, and the dates of her births (up to 20 births3

). This 

provides a total of 564,686 observations. 

The surveys included are all Standard DHS with samples representative of the entire female 

population.4

 A few countries with DHS between 1986 and 2006 were excluded due to comparability 

issues. The only DHS in Sudan was conducted in 1990, and included only ever-married women; hence, 

the Sudan is excluded from this study. The 1999 Senegal DHS is listed as a Standard DHS but is not 

coded in the same manner as the other surveys. In order to avoid any possible errors in re-coding, this 

survey is also excluded. Also, the Ethiopia surveys have dates listed in the Ethiopian calendar. Rather 

than risk coding problems from making these compatible with the rest of the surveys, Ethiopia is also 

excluded. Finally, I do not include Mauritania and Eritrea because the data’s use is restricted. 

 

3

 The Madagascar 1997 survey contains data on the number of births up to 21. Because women with 21 births 

represent a very small sample and in order to be comparable to other surveys, the number of births is capped at 20 

for this country and year. 

4

 DHS surveys that interviewed only ever-married women were excluded from this analysis.
Table 2.1: Sample sizes of DHS fertility data used, by country and survey year 

Country 

Survey Year 

1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 

Benin 5,491 6,219 18,000 Burkina Faso 6,354 6,445 12,477 Burundi 3,970 Cameroon 3,871 5,501 10,656 Central African Republic 5,884 Chad 7,454 6,085 Comoros 3,050 Congo (Brazzaville) 7,051 Côte d'Ivoire 8,099 3,040 Gabon 6,183 Ghana 4,488 4,562 4,843 5,691 Guinea 6,753 7,954 Kenya 7,150 7,540 7,881 8,195 Lesotho 7,095 Liberia 7,092 Madagascar 6,260 7,060 7,949 Malawi 4,850 13,220 11,698 Mali 3,200 9,704 12,817 14,583 Mozambique 8,779 12,418 Namibia 5,421 6,755 Niger 6,503 7,577 9,223 Nigeria 8,781 9,810 7,620 Rwanda 6,551 10,421 11,321 Senegal 4,415 6,310 8,593 14,602 South Africa 11,735 Tanzania 9,238 8,120 10,329 Togo 3,360 8,569 Uganda 4,730 7,070 7,246 8,531 Zambia 7,060 8,021 7,658 Zimbabwe 4,201 6,128 5,907 8,907 

6 
7 

2.2 Panel Creation 

The collection of women’s birth histories in the DHS enables the creation of panel data. Creation 

of the panel involves establishing multiple records for each woman based on information that a woman 

has provided in a single survey about her fertility history. From the individual-level records, I create 

panel data of each woman representing her entire fertility history between age 15 and the year of the 

survey.5

 A panel data set contains multiple records for the same individuals over time. The observation 

is a person-year. 

This panel created from fertility histories is different than the synthetic panels that are often 

constructed from period measures. In these synthetic panels, different people represent a group over time. 

For example, suppose two surveys are conducted, one in 1990 and the other in 1995, covering different 

women each year. Using the 1990 survey, a statistic is calculated for women who are 20 years old in 

1990. The same statistic is calculated using the 1995 survey for women who are age 25 in 1995. These 

two statistics might then be linked to show how women born in 1970 behave as they age. However, the 

same women are not interviewed in 1990 and 1995. While this is a perfectly reasonable method of 

estimating changes over time, it is not the method that I employ. Instead, the fertility histories allow the 

calculation of fertility rates as if the same women had been interviewed in 1990 and 1995. 

To make years comparable requires picking a reference point. I choose the end of the calendar 

year. Therefore, I define a woman’s age as the number of completed years of life at the end of the 

calendar year. The woman’s number of births is the number that she has had by the end of the calendar 

year. 

To illustrate creation of the panel, consider an example. Suppose the 1996 Benin survey contains 

information on a woman age 25 who was born in November 1971 and who has given birth three times. 

For simplicity, suppose that all three births occurred in November but in different years, say 1995, 1993, 

and 1991. Also assume that the respondent was interviewed in December 1996. Table 2.2 below shows 

the information in the DHS survey for this woman, named “Respondent 1.” In order to create a panel, I 

make 10 other records for this woman. I make a record for her in 1995 in which is she is age 24, gives 

birth during the year, and has two prior births. This process continues until the beginning of her 

reproductive years, which I assume (following the DHS) to be age 15. At the end of 1986, the woman is 

age 15 and has not given birth at all. I do not make a record for the respondent in 1985 or any other 

earlier year, nor do I make a record for the respondent for 1997 or any other later year. 

To further illustrate the concept, consider a second example for “Respondent 2.” This respondent 

does not have her births in the same month. Further, this example demonstrates where this study’s

method will create discrepancies between births by age according to the respondent’s years of life lived 

versus age at the end of the calendar year. Suppose this respondent was also interviewed in December, 

1996. Respondent 2’s date of birth is June, 1975, so that at the time of the interview she is age 21. 

Suppose that this respondent has had two births, one in January, 1994, and a previous one in May, 1992. 

At the end of 1994, the respondent is age 19 and has had a total of two births. At the end of 1992 the 

respondent is age 17 and has had one birth. Note that the respondent is 16 when she gives birth to her 

first child, but I code her as age 17 for this first birth. 

 

 

5

 The youngest age recorded in DHS surveys is 12. In creating the cumulative number of births by a given age and 

the age at first birth, I include births that occurred before age 15, but I do not show ASFRs for ages below 15. 
8 

Table 2.2: Example of panel creation 

Respondent 1 

Date of Respondent’s Birth: Nov., 1971. Date of Interview: Dec., 1996. 

Date of Birth 1: Nov., 1995. 

Date of Birth 2: Nov., 1993. 

Date of Birth 3: Nov., 1991. 

Year: 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986 

Age at end of 

year 

25 24 23 22 21 20 19 18 17 16 15 

Number of 

births within 

year 

0 1 0 1 0 1 0 0 0 0 0 

Total number 

of births 3 3 2 2 1 1 0 0 0 0 0 

Respondent 2 

Date of Respondent’s Birth: June, 1975. Date of Interview: Dec., 1996. 

Date of Birth 1: Jan., 1994. 

Date of Birth 2: May, 1992. 

Year: 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986 

Age at end of 

year 

21 20 19 18 17 16 15 - - - - 

Number of 

births within 

year 

0 0 1 0 1 0 0 - - - - 

Total number 

of births 2 2 2 1 1 0 0 - - - - 

Performing this process for all observations yields over 7.5 million person-year observations. 

Table 2.3 provides the ranges of years covered for each country in the panel data set. 

Because the interview year only contains information for the calendar year between January and 

the month of the interview, the full year of the interview is not covered. Rather than attempting to impute 

fertility rates for the remaining months after the interview, I exclude data from the actual interview year. 

Finally, in calculating fertility statistics, observations are weighted according to relative 

probability of responding to the DHS, the individual DHS sample sizes within countries, and the relative 

population sizes of countries. See Appendix A for a detailed description of the weighting method. 
9 

Table 2.3: Years covered by DHS surveys and by panel

Country

Earliest 

survey year 

Latest 

survey year 

Earliest 

women’s birth 

year possible 

in panel 

Latest 

women’s birth 

year possible 

in panel 

Earliest 

possible year 

of data in panel 

Latest possible 

year of data in 

panel 

Benin 1996 2006 1946 1990 1961 2005 

Burkina Faso 1992 2003 1942 1987 1957 2002 

Burundi 1987 1987 1937 1971 1952 1986 

Cameroon 1991 2004 1941 1988 1956 2003 

Central African 

Republic 1994 1995 1944 1979 1959 1994 

Chad 1996 2004 1946 1988 1961 2003 

Comoros 1996 1996 1946 1980 1961 1995 

Congo 

(Brazzaville) 2005 2005 1955 1989 1970 2004 

Côte D’Ivoire 1994 1999 1944 1983 1959 1998 

Gabon 2000 2000 1950 1984 1965 1999 

Ghana 1988 2003 1938 1987 1953 2002 

Guinea 1999 2005 1949 1989 1964 2004 

Kenya 1989 2003 1939 1987 1954 2002 

Lesotho 2004 2004 1954 1988 1969 2003 

Liberia 1986 1986 1936 1970 1951 1985 

Madagascar 1992 2004 1942 1988 1957 2003 

Malawi 1992 2004 1942 1988 1957 2003 

Mali 1987 2006 1937 1990 1952 2005 

Mozambique 1997 2003 1947 1987 1962 2002 

Namibia 1992 2000 1942 1984 1957 1999 

Niger 1992 2006 1942 1990 1957 2005 

Nigeria 1990 2003 1940 1987 1955 2002 

Rwanda 1992 2005 1942 1989 1957 2004 

Senegal 1986 2006 1936 1990 1951 2004 

South Africa 1998 1998 1948 1982 1963 1997 

Tanzania 1992 2004 1942 1988 1957 2003 

Togo 1988 1998 1938 1982 1953 1997 

Uganda 1988 2006 1938 1990 1953 2005 

Zambia 1992 2002 1942 1986 1957 2001 

Zimbabwe 1988 2006 1938 1990 1953 2005 
10 

2.3 Data Limitations

The primary limitation of the data arises from the potential of a sample gathered at one point in 

time to misrepresent the population in other points in time. In creating the panel described above, I must 

assume that the population characteristics in the year in which the survey was conducted are similar to the 

characteristics of the population in prior years. 

Suppose, for example, that a country has a DHS conducted in 2000. The sampling required to 

create a representative sample for the survey is based on the characteristics of the population in 2000. 

Most notably, these characteristics include women’s ages. In the analyses in this report, however, I use 

the birth histories of women who are age 40 in 2000 to characterize fertility rates of women age 25 in 

1985. If women age 40 in 2000 have different birth patterns than the full distribution of women age 25 in 

1985, then bias may be introduced. 

This bias could arise if women with certain fertility patterns are more likely than other women to 

die young. For example, suppose the distribution of women who are age 25 in 1985 includes two types of 

women: women who would have low completed fertility if they were to survive through their 

childbearing years, and women who would have high completed fertility if they were to do the same. If 

only the low-fertility women survive to 2000, then using this sample to characterize the age-specific 

fertility for women age 25 in 1985 would underestimate the fertility rates of that year. 

Fertility-specific mortality may bias results in either direction. It is plausible that high-fertility 

women might have a higher probability of death during childbirth. Given that sub-Saharan countries have 

the highest maternal mortality rates in the world (WHO, UNICEF, UNFPA, and the World Bank, 2007), 

differential mortality by fertility status may be a significant data problem in the analysis. Alternatively, if 

women who have diseases (such as HIV) that make them less able to conceive also have a higher 

probability of early death from these diseases, this fact could lead to lower-fertility women dying younger 

than higher-fertility women. 

The longer the time between the DHS survey and the year for which I am computing data, the 

higher the likelihood that the distribution may be biased. For example, using women age 40 in 2000 to 

characterize the birth rates of women age 35 in 1995 will probably suffer less bias than using these same 

women to characterize the birth rates of women age 15 in 1975. Therefore, countries with multiple DHS 

surveys will have more complete information, and data years that are closer to the survey years will have 

better estimates than those far from the survey years. 

While these biases may be minor in many cases, they may be more pronounced in countries with 

high HIV prevalence or high maternal mortality. I do not attempt to correct statistics for these biases, due 

to difficulties arising from lack of mortality records. While maternal mortality has been estimated in 

many of the countries studied, there is much uncertainty in these estimates (see WHO and UNICEF, 

1996; WHO, 1997). Readers are therefore cautioned that such biases may exist and that results may 

reflect these biases rather than actual trends. 

While the use of the retrospective birth histories is common in performing fertility analyses (see, 

for example, Rutstein and Rojas, 2006), the window of retrospective data used is usually 3 to 5 years. I 

use a longer window of time before each survey (up to 34 years). Thus the biases may be more likely to 

affect the analyses in this study compared with other retrospective studies. 
11 

3 Fertility Trends by Mother’s Birth Cohort

This section presents figures that show completed fertility by women’s birth cohort. They show 

that in the majority of countries in this study completed fertility decreases with each successive cohort. 

3.1 Cumulative Number of Births by Mother’s Birth Cohort 

Examination of cumulative number of births by age and cohort for the 30 sub-Saharan African 

countries studied can provide evidence of fertility transition—the extent to which fertility decline has 

occurred, and whether the decline has stalled or reversed. For women who have completed their 

reproductive years, the cumulative number of births represents cohort TFR, or the completed number of 

births. For cohorts that have not yet reached the end of their childbearing years, I can construct the 

cumulative rates for the available ages, to provide a projection of completed fertility. 

Due to differing time coverage of the DHS surveys, I focus only on 23 countries when 

performing the grouped analysis.6

 These 23 countries have the most comparable coverage of the same 

cohorts and age groups. For these countries, I examine only the cohorts born in 1940-1949, 1950-1959, 

1960-1969, and 1970-1979. For the cohorts born in 1940-1949 and 1950-1959, I examine all age groups 

between 15 and 49. For the cohort born between 1960 and 1969, I examine age groups between 15 and 

39. For the cohort born between 1970 and 1979, I examine age groups between 15 and 29. I exclude for 

this pooled analysis the cohort born between 1980 and 1989 in order to include more countries. 

Figure 3.1 shows the cumulative number of births over the reproductive years for successive 

cohorts in all 23 countries combined. Each curve represents a cohort of women born in a particular range 

of years. The earliest cohort is 1940-1949, represented by the upper-most curve.7

 For women born 

between 1940 and 1949, the average cumulative number of births by age 45-49 is 7.2. The curve for the 

1970 to 1979 cohort shows data only up to age 25-29, reflecting the fact that data are not yet available for 

this cohort at later ages. However, an indication of the cohort’s completed fertility is suggested by 

following the trajectory of that cohort’s curve to the later ages.

For each successive cohort shown in Figure 3.1, the curves shift downward consistently, 

reflecting lower fertility for each successive cohort of women, but the declines are not large. There 

appears to be no indication in Figure 3.1 that the fertility transition is reversing, in which case later 

cohorts would have curves higher than those of earlier cohorts. 

Tempo effects may also be reflected in these curves; however, no tempo effect is evident from the 

pooled data (Figure 3.1). Suppose two successive cohorts have the same completed fertility. A tempo 

effect will be evident if the later cohort curve diverges from the prior cohort’s curve for one age group 

and then returns to the prior cohort’s curve.8

 

 

 

6

 The excluded countries are the Central African Republic, Burundi, the Congo, Gabon, Lesotho, Liberia, and 

Nigeria. Appendix B includes individual country-level analysis for these countries as well as the others. 

7

 While the panel data allow for observations on women born between 1936 and 1939, I exclude them due to small 

sample size and non-equivalent size of the cohort. 

8 This describes a tempo effect without a “quantum” effect.
12 

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age Group

Figure 3.1: 23 Sub-Saharan African countries: Cumulative number of births,

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Birth curves for individual countries reveal differences between countries, as well as between 

successive cohorts. Twenty-eight of the 30 countries studied display at least some fertility decline. The 

two that do not are the Central African Republic and Mali. Additionally, the declines for Guinea and 

Liberia are very small. The figures for each of the 30 countries appear in Appendix B. 

3.2 Age-Specific Fertility Rates by Mother’s Birth Cohort

Another indication of fertility trends can be found in age-specific fertility rates. Figure 3.2 shows 

the trends in ASFRs by mother’s birth cohort for the same cohorts as in Figure 3.1. This shows a variant 

of the same data, but the number of births is not cumulative, which enables one to examine differences 

between cohorts that are not compounded with age and thus to study the ages at which fertility declines 

have been most likely to occur. 

Figure 3.2 shows a decline in births by age between women of successive birth cohorts. Further, 

the differences between cohorts appear to be getting larger. The difference in fertility between the 1940-

1949 and the 1950-1959 cohorts appears smaller than the difference between the 1960-1969 and 1970-

1979 cohorts. 
13 

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Fig. 3.2: 23 Sub-Saharan African countries: 

Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

To further examine the changes in fertility between cohorts, I calculate the differences between 

ASFRs by cohort and calculate whether the rates are statistically significantly different between cohorts. 

Table 3.1 provides the means, standard deviations, and sample sizes of the data shown in Figure 3.2. “N” 

denotes the weighted sample sizes according (see Appendix A for description of weights). 

 
14 

Table 3.1: 23 Sub-Saharan African countries: Age-specific fertility rates by mother's age 

group and birth cohort

Age group 

Mother's Birth Cohort 

1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.83 0.78 0.74 0.62 

Std. dev. (0.09) (0.02) (0.01) (0.04) 

 N 63,861 318,213 579,916 652,283 

20-24 Mean 1.49 1.47 1.40 1.30 

Std. dev. (0.10) (0.03) (0.04) (0.07) 

 N 67,078 319,381 548,044 426,012 

25-29 Mean 1.56 1.52 1.41 1.32 

Std. dev. (0.12) (0.03) (0.06) (0.12) 

 N 67,065 316,319 450,867 174,174 

30-34 Mean 1.43 1.33 1.22 

Std. dev. (0.12) (0.05) (0.06) 

 N 67,090 293,639 284,228 

35-39 Mean 1.11 0.98 0.93 

Std. dev. (0.10) (0.06) (0.10) 

 N 65,633 230,965 114,260 

40-44 Mean 0.61 0.54 

Std. dev. (0.11) (0.07) 

 N 50,076 128,289 

45-49 Mean 0.22 0.19 

Std. dev. (0.15) (0.13) 

 N 15,379 26,933 
15 

Table 3.2 shows the differences in fertility by age between cohorts. For simplicity, and because 

of smaller sample sizes in the earliest and latest cohorts (1936-1939 and 1980-1989, respectively), I focus 

only on the four cohorts born between 1940 and 1979. Allow two successive cohorts to be denoted c1

and c2. Let c2 be later than c1. The difference between age-specific fertility rates between cohorts is 

therefore: 

(E.1) ASFR ASFR a c, 2  a c, 1

While the difference between the rates allows one to see the level change, the ratio of age-specific 

fertility rates between cohorts allows one to view percentage differences. The ratio is calculated: 

(E.2) , 2

, 1, 2

, 1

a c

ac c

a c

ASFR

r

ASFR 

If , 1, 2 1 ac c r  then ASFR ASFR a c, 2  a c, 1 . The percentage difference is , 1, 2 (1 )*100 ac c   r . 

As an example of how to read Table 3.2, the ASFR for women age 15-19 declined by 0.05 of a 

child between the 1940-1949 and 1950-1959 cohorts—a 6% decline. Further, the difference between the 

rates is statistically significant at the 95% level, as evidenced by a t-statistic with an absolute value greater 

than 1.96. The right-most column shows the average; for example, the ASFR for women age 15-19 

declined 9% between successive cohorts, on average. A ratio of greater than 1.0 means that the ASFR for 

that age group increased between successive cohorts. Likewise, a ratio less than 1.0 means that the ASFR 

for that age group decreased between successive cohorts. The bottom rows show the average differences 

between cohorts. For example, the average difference by age group between the 1940-1949 and 1950-

1959 cohorts was 0.06 of a child, or 8%. 

Examination of changes in ASFRs indicates whether fertility changes are more likely in particular 

age groups. The declines by age are largest in level among women aged 30-34. Percentage-wise, the 

largest declines appear in ages 15-19 and ages over 40. Given these are the lowest fertility ages, larger 

percentage changes can occur with smaller declines in fertility. However, changes cannot be witnessed 

for the later age groups and later cohorts. While in the earlier cohorts changes are larger among the older 

age groups, in later cohorts there are large declines amongst the youngest age group. This might be 

indicative of a pattern in which older women lower their fertility rates first, followed by changes in the 

younger age groups. 

While the 1970-1979 cohort has not yet ended the reproductive years, I can compare each cohort 

up to age 29. In doing this, the largest fertility differences are between the 1960-1969 and the 1970-1979 

cohorts. There is a 10% decline between these cohorts (or 0.11 of a birth). If one uses the 10% decline 

benchmark that characterizes fertility transition (Coale and Watkns, 1986), the table suggests that in these 

pooled data from 23 sub-Saharan African countries, fertility transition started between the 1960-1969 and 

1970-1979 cohorts. 

Finally, these fertility declines between cohorts are always statistically significant, suggesting that 

the differences between cohorts are unlikely to be the result of random variation in the ASFRs. 

 
16 

Table 3.2: 23 Sub-Saharan African countries: Differences in age-specific fertility rates between 

mothers' birth cohorts 

Age group 

 

Mothers' Birth Cohort 

Average 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 

15-19 Difference in means -0.05 -0.04 -0.12 -0.07 

Ratio of means 0.94 0.95 0.84 0.91 

 T-statistic for difference between means (147.16) (955.96) (2,380.74) 

20-24 Difference in means -0.02 -0.07 -0.10 -0.07 

Ratio of means 0.98 0.95 0.93 0.95 

 T-statistic for difference between means (60.22) (964.84) (934.17) 

25-29 Difference in means -0.04 -0.10 -0.09 -0.08 

Ratio of means 0.97 0.93 0.93 0.95 

 T-statistic for difference between means (85.65) (1,028.72) (321.51) 

30-34 Difference in means -0.10 -0.11 -0.10 

Ratio of means 0.93 0.92 0.92 

 T-statistic for difference between means (204.90) (711.21) 

35-39 Difference in means -0.13 -0.05 -0.09 

Ratio of means 0.89 0.95 0.92 

 T-statistic for difference between means (313.09) (143.54) 

40-44 Difference in means -0.07 -0.07 

Ratio of means 0.89 0.89 

 T-statistic for difference between means (127.32) 

45-49 Difference in means -0.03 -0.03 

Ratio of means 0.87 0.87 

 T-statistic for difference between means (20.10) 

Average of means: All ages -0.06 -0.07 -0.11 

Average ratio: All ages 0.92 0.94 0.90 

Average of means: Ages 15-29 -0.04 -0.07 -0.11 

Average ratio: Ages 15-29 0.97 0.94 0.90 

 
17 

Using pooled data masks differences between countries. ASFR data by cohort for each country 

appear in Appendix B. Table 3.3 presents the mean percentage differences between cohorts in ASFRs for 

ages 15-29 for each country. Older age groups are excluded so that more countries and cohorts can be 

included in the comparison. Examining these changes between cohorts suggests that of the 13 countries 

with a decline between the 1940-1949 and 1950-1959 cohorts, 11 show larger declines with successive 

cohorts. Of the 10 countries that begin with increases or no changes in fertility between cohorts, 8 switch 

by the third cohort difference to either small decreases or constant fertility. This pattern of declining 

cohort fertility for women born after 1950 is also found by Garenne (2008). The only exceptions to this 

pattern are Mali and the Central African Republic, which exhibit small fertility increases between cohorts. 

Examination of Table 3.3 can provide an indication of which countries have started the fertility 

transition, using the benchmark of a 10% decline in fertility. Of the 30 countries studied, 4 (Benin, 

Ghana, Rwanda, and South Africa) show at least a 10% decline in fertility between the 1940-1949 and 

1950-1959 cohorts. Fourteen countries have at least 10% declines between the 1950-1959 and 1960-1969 

cohorts. No country shows sustained increasing fertility after a decline. Thus there do not appear to be 

any unconditional “reversals” in fertility transition. 

A stall in fertility decline would be indicated by a country showing no declines after prior fertility 

declines, or by fertility declining at a slower pace than before. While no country exhibits constant fertility 

after a period of decline using the statistics in Table 3.3, two countries show slowing fertility declines. 

These include the Congo (Brazzaville) and Madagascar. These are not the countries found by other 

researchers to be experiencing stalls in fertility decline (see, for example, Garenne, 2008). Garenne, 

examining period measures, finds stalls fertility decline in Ghana, Kenya, Nigeria, Rwanda, and Tanzania 

between 1995 and 2005. While the data grouped for ages 15-29 do not reflect stalls in fertility decline 

for these countries, examination of data for individual age groups from the individual countries does. For 

example, Kenya, Nigeria, Rwanda, and Tanzania all show increases in fertility between the 1960-1969 

and 1970-1979 cohorts for the 30-34 age group. Ghana shows a much slower fertility decline for this 

same age group and cohort difference (see Appendix B). 

Table 3.4 explores which age groups have experienced the largest declines in fertility between 

cohorts. These numbers are derived from the tables in Appendix B that look like Table 3.2. For example, 

for women age 20-24 the average ratio of means in Table 3.2 is 0.95, which in Table 3.4 appears as a 5% 

decline. Table 3.4 shows that, between women born in 1940 and those born in 1979, the group with the 

largest fertility decline is age 15-19. This finding suggests a delay in the start of childbearing among 

younger women. After this youngest age group, countries exhibit either similar or increasing fertility 

declines by age group. Several countries show average increases for age 20-24 and 25-29. Chad, 

Malawi, Mali, Mozambique, and Niger all show average fertility increases for age 20-24. 

The biases potentially arising from retrospective data would mean that women who give birth 

later or who have fewer births are disproportionately represented in the data. To the extent that there is 

this type of bias in the data, it would yield overestimates of changes at older ages. This supports the 

finding that the largest percentage declines in fertility are among the youngest age groups. 
18 

Table 3.3: Percentage difference between cohorts in average age-specific 

fertility rates for ages 15-29. 

Country

Difference between mother's birth cohorts 

1940-1949 to 

1950-1959 

1950-1959 to 

1960-1969 

1960-1969 to 

1970-1979 

23 Pooled Countries -3% -6% -10% 

Benin -11% -2% -13% 

Burkina Faso 3% 0% -12% 

Burundi -1% -17% 

Cameroon 3% 1% -17% 

Central African Republic 0% 2% 

Chad 4% -5% 

Comoros -17% 

Congo (Brazzaville) -22% -10% 

Côte D’Ivoire 4% -4% -22% 

Gabon -12% -16% 

Ghana -10% -10% -21% 

Guinea 1% -2% 

Kenya -1% -13% -23% 

Lesotho -12% -14% 

Liberia 2% 

Madagascar -8% -10% -9% 

Mali 3% 1% 1% 

Malawi 6% -2% -9% 

Mozambique 5% -1% -3% 

Namibia -1% -11% -20% 

Niger 5% 5% -8% 

Nigeria 5% -3% -13% 

Rwanda -16% -10% -13% 

Senegal -5% -10% -19% 

South Africa -12% -6% -15% 

Tanzania 0% -12% -14% 

Togo -1% -10% -20% 

Uganda -3% -3% -3% 

Zambia -4% -13% -14% 

Zimbabwe -5% -16% -20% 

Notes: Missing observations occur due to missing data. Statistics calculated by 

averaging changes between cohorts for age groups 15-19, 20-24, and 25-29. No 

adjustment is made for relative size of age group.
19 

Table 3.4: Percentage difference between cohorts born between 1940 and 1979 in agespecific fertility rates

Country

Age group 

15-19 20-24 25-29 30-34 

23 Pooled Countries -9% -5% -5% 

Benin -13% -6% -7% -6% 

Burkina Faso -2% -1% -6% -8% 

Cameroon -7% -1% -5% -3% 

Central African Republic -7% 0% 

Chad -3% 2% 3% -2% 

Cote d'Ivoire -7% -5% -9% 

Ghana -18% -11% -11% -11% 

Kenya -19% -8% -10% -9% 

Madagascar -13% -6% -8% -9% 

Mali 1% 3% 1% -3% 

Malawi -1% 2% -5% -6% 

Mozambique -1% 4% -1% 0% 

Namibia -7% -10% -16% 

Niger 1% 2% -2% -4% 

Nigeria -5% -4% -3% 0% 

Rwanda -21% -10% -8% -7% 

Senegal -16% -11% -8% -7% 

South Africa -7% -16% -10% 

Tanzania -18% -5% -4% -6% 

Togo -16% -9% -7% 

Uganda -9% 0% -1% -1% 

Zambia -16% -7% -9% -4% 

Zimbabwe -18% -11% -13% -16% 

Notes: Countries with missing data are not shown. Statistic calculated by averaging differences 

between 1940-1949 and 1950-1959 cohorts, 1950-1959 and 1960-1060 cohorts, and 1960-1969 

and 1970-1979 cohorts. 

21 

4 Discussion and Conclusions

This report has provided a comparative analysis of fertility trends in 30 sub-Saharan African 

countries, using data from 74 DHS conducted between 1986 and 2006. Unlike much work on fertility 

trends, this report examines fertility trends by mother’s birth cohort. The goal has been to address four 

main questions. First, what countries are experiencing fertility declines, and at what rates? Second, is the 

stalling in fertility transition that other studies have suggested also found in cohort measures? Third, 

between what cohorts is fertility decline largest? Fourth, is fertility declining differently at different ages, 

and if so, which ages experience larger declines? 

With regard to the first question, all of the 30 countries studied exhibit at least some indications 

of fertility decline. In nearly all of the countries fertility rates have declined between mother’s birth 

cohorts, starting with women born in 1960-1969. Countries with fertility increases between earlier 

cohorts have switched to at least small declines by later cohorts. The only exceptions to this pattern are 

Mali and the Central African Republic, which shows few signs of fertility decline. 

As to the second question, the measures examined show little evidence of a “reversal” of fertility 

transition. Several countries, however, exhibit what could be a slowing or even reversal of fertility 

decline between cohorts, at least for certain age groups. The Congo (Brazzaville) and Madagascar show 

slowing fertility declines. Ghana, Kenya, Rwanda, and Tanzania all show increases in fertility between 

the 1960-1969 and 1970-1979 cohorts for the 30-34 age group. Between the 1940-1949 and 1960-1969 

cohorts, many countries also exhibit increasing fertility, particularly for groups under age 25. However, 

by later cohorts most countries show the largest percentage fertility declines in the 15-19 age group, 

suggesting a delay in the start of childbearing. The overall pattern is that countries that have initiated 

declines do not later see sustained increases in fertility. 

 While countries vary in fertility levels and trends, 26 of the 30 countries studied show at least a 

10% decline in fertility for at least one age group between the 1950-1959 and 1960-1969 cohorts; a 10% 

decline in fertility is the level usually cited as evidence of the start of fertility transition. This provides an 

answer to the first question. Since most countries did not exhibit a 10% decline between the cohorts born 

in 1940-1949 and 1950-1959, it is possible to state, using this study’s data, that fertility transition began 

with the 1960-1969 cohort. 

As to the fourth question, beyond the youngest age group, most countries exhibit sustained or 

progressively larger fertility declines in age groups between 20 and 34. This findings suggests that 

fertility decline began with women later in their reproductive years (age 25 and over), followed by 

younger age groups. 

The goal of this report has been to present basic trends in specific fertility measures, with an 

emphasis on cohort measures. Because the data show cohort trends, they may paint a different picture 

than period trends. This report includes a great deal of data that has not been emphasized, particularly at 

the country level (see Appendix B), but that can be useful for researchers and policy-makers. Further 

work should test the robustness of the trends studied with cohort measures, and examine how they relate 

to trends identified using different measures. 

23 

References

Bongaarts, J. 2002. The End of the Fertility Transition in the Developed World. Population and 

Development Review 28(3): 419-443. 

Cleland, J., N. Onuoha, and I. Timaeus. 1994. Fertility Change in Sub-Saharan Africa: A Review of the 

Evidence. In T Locoh and V Hertrich (eds.), The Onset of Fertility Transition in Sub-Saharan Africa. 

Liege, Belgium: Derouaux Ordina. 

Coale, A. and S.C. Watkins (eds.). 1986. The Decline in Fertility in Europe. Princeton: Princeton 

University Press. 

Garenne, M. 2008. Fertility Changes in Sub-Saharan Africa. DHS Comparative Reports. Calverton, 

MD: Macro International, Inc. 

Rutstein, S.O. and G. Rojas. 2006. Guide to DHS Statistics. Demographic and Health Surveys. 

Calverton, MD: ORC Macro. 

WHO, UNICEF, UNFPA, and The World Bank. 2007. Maternal Mortality in 2005: Estimates 

developed by WHO, UNICEF, UNFPA, and the World Bank. Geneva, Switzerland: WHO Press. 

25 

Appendix A: Construction of Sample Weights

DHS surveys are designed to be representative of the overall household population. Accuracy of 

statistics is lower in smaller sample sizes. If individuals are randomly selected from the entire population 

to be surveyed, the number of survey observations for a group that constitutes a smaller proportion of the 

overall population would be very small. This would lead to potentially inaccurate estimates for this 

group. In this case a survey may oversample this group, so that the group’s sample proportion is larger 

than the group’s proportion in the population. The survey then provides sample weights to data users so 

that these over-sampled individuals can be statistically made to represent their actual portion of the 

population. For example, urban women may constitute 10% of the population, but may constitute 50% of 

the sample. Urban women would then have sample weights such that they would “appear” as 10% of the 

sample. 

The DHS provides individual weights that can be used to make sample statistics representative of 

the population. Summing across the sample weights for each survey yields the total number of 

observations in the survey. The DHS sample is performed in order to be representative of the population 

at the time it was taken. 

While the DHS sample weights are useful in creating population-representative samples for the 

time of the survey, further weighting is necessary in creating sample statistics with the constructed panel. 

The first problem is that observations from several surveys for an individual country are combined in the 

creation of the panel. 

The second problem is that DHS samples range in size but are not reflective of the overall 

population size. Two countries may each have a DHS survey size of 3,000, but one country may have a 

population of 1 million while the other has a population of 10 million. Combining the samples from these 

two countries will make them appear to be equally in weight, even though the country with more people 

is more representative of the total population of both countries combined. 

To deal with these issues and to create new weights that are useful for the purposes of this study, I 

construct a new weight composed of two parts. The first part is the DHS sample weight. The second part 

is used to weight individual women to make the sample reflective of the country’s population size and age 

distribution in a particular year. 

A.1 Weights for Analyses of Individual Countries 

The construction of the weights for analyses of individual countries begins with the DHS sample 

weights. Each respondent is assigned a sample weight for the particular survey. Allow i to denote the 

individual, D to index the DHS surveys in an individual country C, and z be the total number of surveys 

in country C. Refer to the sample weight as SWi,D,C. In the panel created from fertility histories, this 

weight remains constant for each individual for all observations on that individual. In essence this is 

saying that individual i represents SWi,D,C women at the time of the survey. The DHS sample weights are 

assigned such that they sum to the DHS sample sizes. 

The second step in the creation of weights for analyses of individual countries is consideration of 

the different DHS sample sizes for an individual country. Consider two people (Person 1 and Person 2) 

who are interviewed in different surveys in the same country. Let Person 1 be interviewed in 1996, while 

Person 2 is interviewed in 1991 (see Table A.1). For this country, suppose that there are only two DHSs, 

so that the 1991 survey is D = 1 while the 1996 survey is D = 2. Further, allow that both individuals were 

born in 1960. In each of their respective surveys, Persons 1 and 2 are assigned DHS sample weights. Let 

Person 1’s sample weight be 1.2 (i.e. SW1,2,C = 1.2), while Person 2’s sample weight is 0.9 (SW1,2,C = 0.9). 
26 

Suppose that the 1996 DHS survey for this country contains 10,000 observations, while the 1991 survey 

contains only 3,000 observations. Allow SSD,C to refer to the sample size for DHS survey D (i.e. SS1,C = 

3,000 and SS2,C = 10,000). 

To understand what percentage each of these individuals should carry in calculated statistics, 

consider the constructed panel. Since both Persons 1 and 2 were born in 1960, after creating the panel, 

there will be observations for each of these individuals for 1990 at age 30. Person 1 is interviewed in 

1996, such that in the panel her age at the end of 1990 is assigned as 30. Person 2 is interviewed in 1991, 

such that in the panel her age at the end of 1990 is also assigned as 30. For simplicity, assume that these 

are the only two observations for age 30 in 1990 for the country in question. Let nA,C,Y be the sample size 

in the panel for age A in country C in year Y. In this example, nA,C,Y = 2. 

If one were to ignore the different DHS sample weights and DHS sample sizes, then each person 

would represent half of the panel sample. However, the individuals have a different likelihood of being 

sampled at the times of their surveys, so I account for this with SWi,D,C. If one were to ignore the 

respective DHS sample sizes, then each individual would account for a proportion of the panel sample for 

age A and year Y equal to 

(E.3) , ,

, ,

1 1

iDC

z n

iDC

D i

SW

SW  



. 

Person 1 would account for 57% of the panel sample, while Person 2 would account for 43%. 

If one takes into account the relative DHS survey sizes for country C, however, the relative 

proportion that each individual accounts for in the panel sample changes. Consider that Person 2 

represents 0.9 people in a DHS sample size of 3,000. However, if the 1991 DHS survey were as large as 

the 1996 DHS survey (10,000), then Person 2 would account for 3.3 people in a survey of 10,000. When 

considering this, it becomes clear that Person 2 should carry more weight in calculated statistics for the 

age group A and year Y than Person 1. To account for this, I employ a scaling factor specific to the survey 

date. Call this scaling factor F1D,C and let 

(E.4) 

,

1

,

,

1

z

D C

D

D C

D C

SS

F

SS

 



When this scaling factor is multiplied by the DHS sample weight (SWi,D,C × F1D,C), Person 2 will 

now account for 71% of the panel sample, while Person 1 only accounts for 29%. 

The weights should sum to the actual panel sample size for the age group, country, and year. The 

scaled DHS sample weights for the two individuals sum to 5.46, not the panel sample size of 2. I 

therefore employ a second scaling factor F2A,C,Y that is constant across individuals in the age group and 

year: 

(E.5) , ,

, ,

,, ,

1

2

( 1)

ACY

ACY n

iDC DC

i

n

F

SW F 



 
27 

Finally, multiplying this second scaling factor by the DHS sample weight and the first scaling 

factor yields the weight W1i,D,A,C,Y used in analyses for individual countries. 

(E.6) ,,,, ,, , ,, 1 1 2 W SW F F iD ACY iDC DC ACY  

Therefore, ,,,, ,,

1

1

n

iD ACY ACY

i

W n



  . The analyses in which this weight is employed appear in 

Appendix B as well as the individual country data in Tables 3.3 and 3.4. 

A further weighting factor is necessary when combining countries. The next section describes 

this additional weight. 

Table A.1: Example of weighting scheme in individual country analyses

Person 1 Person 2 

Sum (where 

relevant) 

Year of interview 1996 1991 -- 

D 2 1 -- 

Year of birth 1960 1960 -- 

Age assigned in panel at end of 1990 30 30 -- 

DHS sample weight (SWi,D,C) 1.2 0.9 2.1 

Proportion of panel sample just accounting for SWi,D,C 57% 43% 100% 

DHS sample size (SSD,C) 10,000 3,000 13,000 

F1D,C 13,000/10,000 13,000/3,000 -- 

SWi,D,C × F1D,C 1.56 3.9 5.46 

Proportion of panel sample accounting for SWi,D,C and SSD,C 29% 71% 100% 

F2A,C,Y 5.46/2 5.46/2 -- 

W1i,D,A,C,Y 0.57 1.43 2 

A.2 Weights for Relative Population Size by Age Group, Country, and Year 

In parts of the analysis different countries are pooled. To reflect relative population sizes, I 

weight observations in this setting using another factor. After the panel has been constructed from the 

individual birth histories, I find the total number of observations in the panel for women of each age 

group in each country in each year between 1950 and 2006. I merge this to population size data for each 

age group, country, and year. Population size data come from the United Nations (UN) estimates. These 

age groups are in five year intervals and range from 15-19 to 45-49. The UN estimates are also only 

available in five-year increments starting in 1950. I create linear projections for each age group and 

country between each five-year increment in order to get estimates for the interim years. 

Let XA,C,Y be the population size by age group (A), country (C), and year (Y). Therefore 

, ,

1

k

ACY

C

X



 is the total population size for all k countries. Likewise, since nA,C,Y is the sample size in the 
28 

panel for an individual country, age group, and year, , ,

1

k

ACY

C

n



 is the summed sample over all countries. 

Since the goal is to weight different countries relative to each other, a third scaling factor (F3) for each 

age group, country, and year is: 

(E.7) 

, ,

, , 1

, .

, , , ,

1

3

k

ACY

ACY C

ACY k

ACY

ACY

C

n X

F

n X





 





The first term in this factor accounts for the relative population size of one country in relation to 

another, while the second term scales the weights so that they sum to the sample size. This is necessary 

so as not to reduce standard deviations on the basis of weights. 

For analyses with pooled data by country, I employ a second weight (W2) which is equal to the 

first weight multiplied by F3: 

(E.8) ,,, ,,, ,, 2 13 W WF i ACY i ACY ACY  

Expanding this formula yields: 

(E.9) 

, ,

,, ,, 1

,,, ,,,,

, , , ,,

1 1

2 1

( 1)

k

ACY

ACY ACY C

i ACY iD ACY D n k

ACY

iD D ACY

i C

n n X

W SW F

n SW F X



 

 	  	 
  
 

    
  
   
   
  




 

Cancelling terms yields: 

(E.10) 

, ,

,,,, 1

,,, ,,

, , ,

1 1

1

2

( 1)

k

ACY

iD ACY D C

i ACY n k ACY

iD D ACY

i C

n SW F

W X

SW F X



 

 	 	


  
 

 



 
 




 

The first term in this equation is the proportion of the total sample weights for the age group, 

country, and year that individual i represents. The second term is the population size by age group, 

country, and year. Multiplying the first two terms together provides an estimate of the number of people 

in the population that person i represents. The third element of the equation provides a scaling factor such 

that the sum of the sample weights will yield the panel sample size (rather than the population size). 

When performing analyses with data grouped over several countries, W2 is employed. The results of 

these analyses appear in Figures 3.1 and 3.2, Tables 3.1 and 3.2, and the statistics for the pooled data in 

Tables 3.3 and 3.4. 
29 

A.3 Impact of Weights in Calculation of Statistics 

A discussion of how the final weights are used in the calculation of statistics is important for 

comprehending their impact. In using the weights and obtaining standard deviations of these estimates 

for testing, I must make slight changes to standard statistics. 

A.3.1 Weighting Age-Specific Fertility Rates 

The age-specific fertility rate is defined as the total number of births to women during the age 

group divided by the total number of women-years spent in the age group. The equation for the 

unweighted ASFR for age group A is: 

(E.11) 

,

1

,

1

n

i A

i

A n

i A

i

B

ASFR

Y











Where Bi,A is the number of births to woman i while in age group A, and Yi,A is the number of 

woman-years spent by woman i in age group A. 

Weighting observations when calculating the ASFRs could follow two approaches. In the first 

approach, one weights births and sums these over the sample, then weights individual woman-years and 

sums these over the sample, and then divides the first sum by the second. Allow wi,A to refer to the weight 

for individual i in age group A. In individual country analyses this weight is W1. In analyses with data 

grouped by country this weight is W2. In this approach the weighted ASFR is: 

(E.12) 

, ,

1

, ,

1

n

iA iA

W i

A n

iA iA

i

w B

ASFR

w Y











This approach follows the standard calculation of the ASFR and maintains the separation between 

births to an individual woman and that individual woman’s contribution to overall woman-years. The 

problem with this approach is that there is no way to calculate a standard deviation. Calculation of a 

standard deviation is necessary if one wants to compare the ASFRs for age group A for two birth cohorts 

of women. I therefore turn to the second approach. 

In the second approach, one calculates the number of births per woman-year for each woman in 

the age group and then weights this quotient. The sum of these weighted quotients divided by the sum of 

the weights is then the ASFR. This second method of calculating a weight ASFR is therefore: 

(E.13) 

,

,

1 ,

,

1

n i A

i A

W i i A

A n

i A

i

B

w

Y

ASFR

w





 	   
      
   
   




30 

If each age interval is one year long, there will be no difference between the first and second 

versions of the weighted ASFR. However, I am looking at 5-year age intervals, so there is a potential for 

slight differences between the two methods. 

Note that the age-specific fertility rates are defined for five-year age groups. Therefore, the sum 

of the weights is over the number of weighted women, not the number of weighted woman-years. 

 To calculate the standard deviation of the second version of the weighted ASFR (in Equation 

(E.13)), let ,

,

,

i A

i A

i A

B

b

Y  . Therefore, 

(E.14) 

  , ,

1

,

1

n

iA iA

W W i

A A n

i A

i

w b

ASFR b

w







 





The standard deviation is 

(E.15) 

2

, ,

1

,

1

( )

W

A

n W

iA iA A

i

ASFR n

i A

i

wb b

s

w













A.3.2 Weighting Cumulative Number of Births by Age Group 

In calculating the cumulative number of births by age group, it is important to point out that I sum 

the weighted ASFRs for ages up to the age group of interest. Thus I calculate the average cumulative 

number of births by age h as 

(E.16) 

1

h

W W

h A

A

C ASFR 

To distinguish this approach from an alternative, consider Equation (E.16) written as 

(E.17) 

  , ,

1

1

,

1

n

h iA iA

W i

h n

A

i A

i

w b

C

w







 

  

  

 

 







An alternative method of calculating the weighted cumulative number of births would be to use 

the stated total number of births and the weight at just age h. This would result in the formula: 
31 

(E.18) 

, ,

1 1

,

1

n h

ih iA

W i A

h n

i h

i

w b

C

w

 



 	


   
 

 



Because this would result in differences when comparing ASFRs and cumulative number of 

births, I do not take this second approach. 

A.3.3 Calculating t-Statistic for Differences between ASFRs by Cohort 

The report contains statistics with which I compare the ASFRs for women born in different time 

periods. In order to test whether the difference between the two ASFRs is statistically significant, I 

calculate a t-statistic. In calculating this, one needs to find the standard deviation of the difference 

between weighted means. Consider two groups of women in the same country born at different times. 

Allow one group of women to be born in cohort Q and the other to be born in cohort P. One would like 

to test for the statistical significance of the difference between ,

W ASFRQ A and ,W ASFRP A . The null and 

alternative hypotheses are: 

(E.19) 0, , : 0 W W H ASFR ASFR Q A   P A

, , : 0 W W H ASFR ASFR A QA PA  

The test statistic is: 

(E.20) , ,

,

W W

Q A P A

Q P

ASFR ASFR

t

s

 

Where 

, ,

2 2

,

, , , ,

1 1

W W ASFRQ A ASFRP A

Q P n m

iQA iPA

i i

s s

s

w w

 

 

 

In the formula for sQ,P, wi,Q,A is the weight for individual i in cohort Q in age group A, n is the 

number of observations in cohort Q in age group A, and m is the number of observations in cohort P in 

age group A. 

Statistics calculated from sample sizes under 250 are suppressed (see Appendix C for suppressed 

ages and cohorts). Since sample sizes will be over 250, the critical value for a 5% confidence level will 

be 1.96. 

33 

Appendix B: Figures and Tables for Individual Countries

Appendix B presents figures for the cumulative and average number of births by mother’s age 

and birth cohort, as well as tables for age-specific birth rates by mother’s cohort and comparisons 

between cohorts. The figures mirror Figures 3.1 and 3.2, and the tables mirror Tables 3.1 and 3.2. When 

a sample for a specific age group, country, and birth cohort had fewer than 250 observations, the statistics 

for it are suppressed, because the small sample sizes may provide misleading statistics. Table C.1 (in 

Appendix C) lists all groups with suppressed statistics. 

 The figures in Appendix B only show data for birth cohorts 1940-1949, 1950-1959, 1960-1969, 

1970-1979, and 1980-1989. Statistics are missing when the country’s surveys do not cover the specific 

cohort and/or age group. While some countries have data for cohorts born between 1940 and/or after 

1989, these statistics are also not shown due to lack of comparability with other cohorts in the time span. 

In the figures for age-specific fertility rates by mother’s birth cohort (Figure B.X.2), if for a 

specific cohort a country only has data for age 15-19 but not age 20-24, then a line showing that cohort’s 

ASFR’s is not shown. This is because the data for the age group 15-19 would only be represented as a 

single dot. In contrast, the figures for cumulative number of births by mother’s age and birth cohort 

(Figure B.X.3) will have the data represented as a line connecting zero to the age 15-19 value. 

In the tables showing comparisons between successive cohorts in age-specific fertility rates 

(Table B.X.2), the difference in means is calculated by subtracting the value for the later cohort from the 

earlier cohort. The ratio is calculated by dividing the value for the later cohort by the value of the earlier 

cohort. 

All statistics are weighted according to W1, as defined in Appendix A. The listed sample sizes 

(“N” in Tables B.X.1) are the number of weighted observations contributing data to the specific age 

group, cohort, and country. These do not denote the number of woman-years covered by the statistics.
34 

B.1 Benin

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.1.1: Benin: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.1.2: Benin: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
35 

Table B.1.1: Benin: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.90 0.67 0.69 0.58 

Std. dev. (1.06) (0.85) (0.86) (0.79) 

 N 314 2,272 663 10,088 

20-24 Mean 1.58 1.46 1.42 1.30 

Std. dev. (0.95) (0.95) (0.94) (0.79) 

 N 314 2,272 6,378 10,088 

25-29 Mean 1.64 1.63 1.51 1.30 

Std. dev. (0.91) (0.92) (0.96) (1.06) 

 N 314 2,272 6,378 8,543 

30-34 Mean 1.48 1.47 1.33 1.25 

Std. dev. (0.89) (0.92) (1.13) (1.47) 

 N 314 2,272 5,207 1,754 

35-39 Mean 1.12 1.10 0.96 

Std. dev. (0.96) (1.02) (1.34) 

 N 314 2,272 3,077 

40-44 Mean 0.70 0.56 0.43 

Std. dev. (0.90) (0.94) (1.02) 

 N 314 1,606 998 

45-49 Mean 0.19 0.21 

Std. dev. (0.57) (0.81) 

 N 314 663 

 
36 

Table B.1.2: Benin: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.23 0.02 -0.12 -0.11 

Ratio of means 0.75 1.03 0.83 0.87 

 T-statistic for difference between means (3.67) (0.59) (3.41) 

20-24 Difference in means -0.12 -0.04 -0.12 -0.09 

Ratio of means 0.93 0.97 0.92 0.94 

 T-statistic for difference between means (2.07) (1.89) (8.11) 

25-29 Difference in means -0.01 -0.11 -0.21 -0.11 

Ratio of means 0.99 0.93 0.86 0.93 

 T-statistic for difference between means (0.19) (4.92) (12.64) 

30-34 Difference in means -0.01 -0.14 -0.08 -0.08 

Ratio of means 0.99 0.90 0.94 0.94 

 T-statistic for difference between means (0.27) (5.79) (2.08) 

35-39 Difference in means -0.02 -0.14 -0.08 

Ratio of means 0.98 0.87 0.93 

 T-statistic for difference between means (0.31) (4.44) 

40-44 Difference in means -0.14 -0.13 -0.14 

Ratio of means 0.80 0.77 0.78 

 T-statistic for difference between means (2.54) (3.29) 

45-49 Difference in means 0.02 0.02 

Ratio of means 1.12 1.12 

 T-statistic for difference between means (0.49) 

 Average of means -0.07 -0.09 -0.13 

Average ratio 0.94 0.91 0.89 
37 

B.2 Burkina Faso

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.2.1: Burkina Faso: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.2.2: Burkina Faso: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
38 

Table B.2.1: Burkina Faso: Age-specific fertility rates by mother's age group 

and birth cohort 

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.70 0.73 0.78 0.64 

Std. dev. (0.83) (0.85) (0.83) (0.78) 

 N 624 3,589 6,733 8,275 

20-24 Mean 1.52 1.59 1.57 1.48 

Std. dev. (1.01) (0.94) (0.87) (1.15) 

 N 624 3,589 6,733 6,022 

25-29 Mean 1.63 1.63 1.56 1.36 

Std. dev. (0.98) (0.88) (1.03) (1.34) 

 N 624 3,589 6,190 2,892 

30-34 Mean 1.59 1.52 1.35 1.24 

Std. dev. (0.95) (0.92) (1.19) (1.56) 

 N 624 3,589 4,420 592 

35-39 Mean 1.33 1.17 1.10 

Std. dev. (0.96) (1.09) (1.32) 

 N 624 3,207 2,215 

40-44 Mean 0.69 0.73 0.61 

Std. dev. (0.82) (1.21) (1.32) 

 N 624 2,133 442 

45-49 Mean 0.24 0.25 

Std. dev. (0.85) (0.83) 

 N 465 810 
39 

Table B.2.2: Burkina Faso: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.03 0.05 -0.14 -0.02 

Ratio of means 1.04 1.06 0.82 0.98 

 T-statistic for difference between means (0.87) (2.67) (10.36) 

20-24 Difference in means 0.08 -0.02 -0.09 -0.01 

Ratio of means 1.05 0.99 0.94 0.99 

 T-statistic for difference between means (1.78) (1.26) (5.04) 

25-29 Difference in means 0.00 -0.07 -0.20 -0.09 

Ratio of means 1.00 0.96 0.87 0.94 

 T-statistic for difference between means (0.10) (3.63) (7.10) 

30-34 Difference in means -0.07 -0.17 -0.11 -0.12 

Ratio of means 0.95 0.89 0.92 0.92 

 T-statistic for difference between means (1.80) (7.12) (1.64) 

35-39 Difference in means -0.16 -0.07 -0.12 

Ratio of means 0.88 0.94 0.91 

 T-statistic for difference between means (3.77) (2.00) 

40-44 Difference in means 0.04 -0.12 -0.04 

Ratio of means 1.06 0.83 0.95 

 T-statistic for difference between means (1.01) (1.77) 

45-49 Difference in means 0.01 0.01 

Ratio of means 1.04 1.04 

 T-statistic for difference between means (0.18) 

 Average of means -0.01 -0.07 -0.13 

Average ratio 1.00 0.95 0.89 
40 

B.3 Burundi 

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.3.1: Burundi: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.3.2: Burundi: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969
41 

Table B.3.1: Burundi: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.48 0.44 0.27 

Std. dev. (0.77) (0.72) (0.57) 

 N 652 1,235 1,627 

20-24 Mean 1.36 1.38 1.25 

Std. dev. (0.99) (0.97) (1.23) 

 N 652 1,235 1,116 

25-29 Mean 1.61 1.64 1.58 

Std. dev. (1.00) (0.91) (1.84) 

 N 652 1,235 310 

30-34 Mean 1.61 1.57 

Std. dev. (0.95) (1.31) 

 N 652 738 

35-39 Mean 1.23 

Std. dev. (0.98) 

 N 652 

40-44 Mean 0.77 

Std. dev. (1.11) 

 N 391 

45-49 Mean 

Std. dev. 

 N 
42 

Table B.3.2: Burundi: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

 to 

1970-1979 Average 

15-19 Difference in means -0.04 -0.17 -0.10 

Ratio of means 0.92 0.62 0.77 

 T-statistic for difference between means (1.00) (6.79) 

20-24 Difference in means 0.02 -0.13 -0.05 

Ratio of means 1.02 0.91 0.96 

 T-statistic for difference between means (0.52) (2.85) 

25-29 Difference in means 0.03 -0.06 -0.01 

Ratio of means 1.02 0.96 0.99 

 T-statistic for difference between means (0.64) (0.55) 

30-34 Difference in means -0.04 -0.04 

Ratio of means 0.97 0.97 

 T-statistic for difference between means (0.68) 

35-39 Difference in means 0.42 0.42 

Ratio of means 1.34 1.34 

 T-statistic for difference between means (2.98) 

40-44 Difference in means 

Ratio of means 

 T-statistic for difference between means 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means 0.08 -0.12 

Average ratio 1.06 0.83 
43 

B.4 Cameroon

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.4.1: Cameroon: Cumulative number of births, 

by mother's age and birth Cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.4.2: Cameroon: Age-specific fertility rates, by mother's birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
44 

Table B.4.1: Cameroon: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.86 0.83 0.90 0.68 

Std. dev. (0.96) (0.90) (0.92) (0.88) 

 N 487 2,327 4,800 6,522 

20-24 Mean 1.31 1.47 1.46 1.25 

Std. dev. (1.06) (1.03) (1.04) (1.32) 

 N 487 2,327 4,800 4,361 

25-29 Mean 1.43 1.44 1.38 1.21 

Std. dev. (1.11) (1.03) (1.15) (1.47) 

 N 487 2,327 3,915 2,358 

30-34 Mean 1.22 1.24 1.08 1.11 

Std. dev. (1.06) (1.08) (1.27) (1.55) 

 N 487 2,327 2,555 574 

35-39 Mean 0.93 0.83 0.73 

Std. dev. (0.99) (1.08) (1.23) 

 N 487 1,787 1,378 

40-44 Mean 0.46 0.43 0.37 

Std. dev. (0.79) (0.95) (0.95) 

 N 487 1,055 338 

45-49 Mean 0.11 0.09 

Std. dev. (0.47) (0.47) 

 N 288 455 
45 

Table B.4.2: Cameroon: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

 to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.03 0.06 -0.22 -0.06 

Ratio of means 0.97 1.08 0.75 0.93 

 T-statistic for difference between means (0.63) (2.77) (12.78) 

20-24 Difference in means 0.16 0.00 -0.21 -0.02 

Ratio of means 1.12 1.00 0.86 0.99 

 T-statistic for difference between means (3.06) (0.11) (8.50) 

25-29 Difference in means 0.02 -0.07 -0.17 -0.07 

Ratio of means 1.01 0.95 0.88 0.95 

 T-statistic for difference between means (0.35) (2.33) (4.79) 

30-34 Difference in means 0.02 -0.16 0.04 -0.04 

Ratio of means 1.01 0.87 1.03 0.97 

 T-statistic for difference between means (0.33) (4.85) (0.54) 

35-39 Difference in means -0.10 -0.10 -0.10 

Ratio of means 0.89 0.88 0.89 

 T-statistic for difference between means (1.92) (2.39) 

40-44 Difference in means -0.03 -0.05 -0.04 

Ratio of means 0.93 0.88 0.91 

 T-statistic for difference between means (0.64) (0.90) 

45-49 Difference in means -0.02 -0.02 

Ratio of means 0.82 0.82 

 T-statistic for difference between means (0.54) 

 Average of means 0.00 -0.05 -0.14 

Average ratio 0.97 0.94 0.88 
46 

B.5 Central African Republic

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.5.1: Central African Republic: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.5.2: Central African Republic: Age-specific fertility rates, 

by mother's birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979
47 

Table B.5.1: Central African Republic: Age-specific fertility rates by 

mother's age group and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.77 0.76 0.77 0.60 

Std. dev. (0.98) (0.90) (0.88) (0.88) 

 N 429 1,164 1,890 2,253 

20-24 Mean 1.26 1.22 1.34 1.23 

Std. dev. (1.12) (1.05) (1.00) (1.45) 

 N 429 1,164 1,890 937 

25-29 Mean 1.24 1.28 1.20 

Std. dev. (1.06) (1.05) (1.23) 

 N 429 1,164 1,753 

30-34 Mean 1.04 1.16 1.04 

Std. dev. (1.03) (1.06) (1.42) 

 N 429 1,164 697 

35-39 Mean 0.83 0.74 

Std. dev. (0.96) (1.12) 

 N 429 1,041 

40-44 Mean 0.48 0.52 

Std. dev. (0.82) (1.22) 

 N 429 383 

45-49 Mean 0.12 

Std. dev. (0.51) 

 N 373 
48 

Table B.5.2: Central African Republic: Differences in age-specific fertility rates between mothers' 

birth cohorts

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.01 0.01 -0.17 -0.06 

Ratio of means 0.98 1.02 0.78 0.93 

 T-statistic for difference between means (0.22) (0.37) (6.20) 

20-24 Difference in means -0.04 0.12 -0.12 -0.01 

Ratio of means 0.97 1.10 0.91 1.00 

 T-statistic for difference between means (0.63) (3.23) (2.18) 

25-29 Difference in means 0.04 -0.07 -0.02 

Ratio of means 1.03 0.94 0.99 

 T-statistic for difference between means (0.67) (1.72) 

30-34 Difference in means 0.11 -0.12 0.00 

Ratio of means 1.11 0.90 1.00 

 T-statistic for difference between means (1.94) (1.91) 

35-39 Difference in means -0.09 -0.09 

Ratio of means 0.89 0.89 

 T-statistic for difference between means (1.55) 

40-44 Difference in means 0.04 0.04 

Ratio of means 1.09 1.09 

 T-statistic for difference between means (0.55) 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means 0.01 -0.01 -0.14 

Average ratio 1.01 0.99 0.85 
49 

B.6 Chad

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.6.1: Chad: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.6.2: Chad: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
50 

Table B.6.1: Chad: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 1.00 1.01 0.99 

Std. dev. (1.04) (0.97) (0.95) 

 N 1,840 3,208 5,023 

20-24 Mean 1.58 1.69 1.62 

Std. dev. (1.04) (0.96) (1.15) 

 N 1,840 3,208 3,979 

25-29 Mean 1.59 1.67 1.54 

Std. dev. (1.01) (0.96) (1.48) 

 N 1,840 3,208 2,315 

30-34 Mean 1.34 1.49 1.34 

Std. dev. (1.04) (1.27) (1.54) 

 N 1,840 2,492 529 

35-39 Mean 0.96 0.98 

Std. dev. (1.01) (1.29) 

 N 1,840 1,381 

40-44 Mean 0.40 0.56 

Std. dev. (0.89) (1.10) 

 N 1,399 316 

45-49 Mean 0.15 

Std. dev. (0.78) 

 N 721 
51 

Table B.6.2: Chad: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

 to 

1950-1959 

1950-1959 

 to 

1960-1969 

1960-1969 

 to 

 1970-1979 Average 

15-19 Difference in means 0.01 -0.02 -0.01 

Ratio of means 1.01 0.98 0.99 

 T-statistic for difference between means (0.28) (1.02) 

20-24 Difference in means 0.11 -0.07 0.02 

Ratio of means 1.07 0.96 1.02 

 T-statistic for difference between means (3.82) (2.76) 

25-29 Difference in means 0.08 -0.12 -0.02 

Ratio of means 1.05 0.93 0.99 

 T-statistic for difference between means (2.66) (3.51) 

30-34 Difference in means 0.15 -0.15 0.00 

Ratio of means 1.11 0.90 1.01 

 T-statistic for difference between means (4.28) (2.12) 

35-39 Difference in means 0.02 0.02 

Ratio of means 1.02 1.02 

 T-statistic for difference between means (0.53) 

40-44 Difference in means 0.16 0.16 

Ratio of means 1.39 1.39 

 T-statistic for difference between means (2.39) 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means 0.09 -0.09 

Average ratio 1.11 0.94 
52 

B.7 Comoros

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.7.1: Comoros: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.7.2: Comoros: Age-specific fertility rates, by mother's birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979
53 

Table B.7.1: Comoros: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.72 0.57 0.34 

Std. dev. (0.99) (0.91) (0.74) 

 N 528 789 1,304 

20-24 Mean 1.39 1.20 0.87 

Std. dev. (1.16) (1.18) (1.27) 

 N 528 789 685 

25-29 Mean 1.56 1.32 

Std. dev. (1.21) (1.21) 

 N 528 789 

30-34 Mean 1.42 1.22 

Std. dev. (1.18) (1.41) 

 N 528 454 

35-39 Mean 1.01 

Std. dev. (1.11) 

 N 528 

40-44 Mean 0.43 

Std. dev. (0.89) 

 N 250 

45-49 Mean 

Std. dev. 

 N 
54 

Table B.7.2: Comoros: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

 to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.15 -0.24 -0.19 

Ratio of means 0.79 0.59 0.69 

 T-statistic for difference between means (2.76) (6.13) 

20-24 Difference in means -0.19 -0.33 -0.26 

Ratio of means 0.86 0.72 0.79 

 T-statistic for difference between means (2.88) (5.18) 

25-29 Difference in means -0.25 -0.25 

Ratio of means 0.84 0.84 

 T-statistic for difference between means (3.60) 

30-34 Difference in means -0.20 -0.20 

Ratio of means 0.86 0.86 

 T-statistic for difference between means (2.38) 

35-39 Difference in means 

Ratio of means 

 T-statistic for difference between means 

40-44 Difference in means 

Ratio of means 

 T-statistic for difference between means 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means -0.20 -0.28 

Average ratio 0.84 0.66 
55 

B.8 Congo

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.8.1: Congo: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.8.2: Congo: Age-specific fertility rates, by mother's birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
56 

Table B.8.1: Congo: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.94 0.67 0.59 

Std. dev. (0.91) (0.77) (0.71) 

 N 344 1,312 2,144 

20-24 Mean 1.43 1.14 1.04 

Std. dev. (0.95) (0.88) (0.83) 

 N 344 1,312 2,144 

25-29 Mean 1.28 1.07 0.96 

Std. dev. (0.92) (0.87) (1.05) 

 N 344 1,312 2,144 

30-34 Mean 1.12 0.89 0.94 

Std. dev. (0.94) (0.84) (1.27) 

 N 344 1,312 935 

35-39 Mean 0.75 0.73 

Std. dev. (0.77) (1.09) 

 N 344 1,312 

40-44 Mean 0.31 0.44 

Std. dev. (0.58) (1.03) 

 N 344 525 

45-49 Mean 0.14 

Std. dev. (0.63) 

 N 344 
57 

Table B.8.2: Congo: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

 1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.27 -0.07 -0.17 

Ratio of means 0.71 0.89 0.80 

 T-statistic for difference between means (5.06) (2.81) 

20-24 Difference in means -0.29 -0.10 -0.20 

Ratio of means 0.80 0.91 0.85 

 T-statistic for difference between means (5.11) (3.39) 

25-29 Difference in means -0.21 -0.11 -0.16 

Ratio of means 0.84 0.90 0.87 

 T-statistic for difference between means (3.74) (3.32) 

30-34 Difference in means -0.23 0.05 -0.09 

Ratio of means 0.80 1.06 0.93 

 T-statistic for difference between means (4.10) (1.04) 

35-39 Difference in means -0.02 -0.02 

Ratio of means 0.98 0.98 

 T-statistic for difference between means (0.32) 

40-44 Difference in means 0.12 0.12 

Ratio of means 1.39 1.39 

 T-statistic for difference between means (2.25) 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means -0.15 -0.06 

Average ratio 0.92 0.94 
58 

B.9 Côte d’Ivoire

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.9.1: Côte d'Ivoire: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.9.2: Côte D'Ivoire: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979
59 

Table B.9.1: Côte D'Ivoire: Age-specific fertility rates by mother's age group 

and birth cohort 

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.83 0.86 0.86 0.64 

Std. dev. (0.98) (0.92) (0.89) (0.84) 

 N 543 1,887 3,410 4,282 

20-24 Mean 1.33 1.41 1.42 1.09 

Std. dev. (1.03) (1.00) (0.93) (1.26) 

 N 543 1,887 3,410 2,610 

25-29 Mean 1.43 1.49 1.30 1.08 

Std. dev. (1.06) (0.98) (1.07) (1.45) 

 N 543 1,887 3,174 695 

30-34 Mean 1.34 1.30 1.07 

Std. dev. (1.03) (1.01) (1.29) 

 N 543 1,887 1,852 

35-39 Mean 1.11 0.96 0.81 

Std. dev. (1.07) (1.11) (1.28) 

 N 543 1,745 465 

40-44 Mean 0.61 0.50 

Std. dev. (0.86) (1.03) 

 N 543 1,022 

45-49 Mean 0.16 0.21 

Std. dev. (0.55) (0.66) 

 N 413 279 
60 

Table B.9.2: Côte D'Ivoire: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

 to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.02 0.00 -0.22 -0.06 

Ratio of means 1.03 1.00 0.75 0.93 

 T-statistic for difference between means (0.47) (0.11) (10.83) 

20-24 Difference in means 0.08 0.00 -0.32 -0.08 

Ratio of means 1.06 1.00 0.77 0.95 

 T-statistic for difference between means (1.67) (0.14) (11.05) 

25-29 Difference in means 0.06 -0.19 -0.22 -0.12 

Ratio of means 1.04 0.87 0.83 0.91 

 T-statistic for difference between means (1.12) (6.34) (3.78) 

30-34 Difference in means -0.04 -0.22 -0.13 

Ratio of means 0.97 0.83 0.90 

 T-statistic for difference between means (0.82) (5.94) 

35-39 Difference in means -0.15 -0.15 -0.15 

Ratio of means 0.86 0.84 0.85 

 T-statistic for difference between means (2.88) (2.33) 

40-44 Difference in means -0.12 -0.12 

Ratio of means 0.81 0.81 

 T-statistic for difference between means (2.37) 

45-49 Difference in means 0.05 0.05 

Ratio of means 1.34 1.34 

 T-statistic for difference between means (1.09) 

 Average of means -0.01 -0.11 -0.25 

Average ratio 1.02 0.91 0.78 
61 

B.10 Gabon

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.10.1: Gabon: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.10.2: Gabon: Age-specific fertility rates, by mother's birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979
62 

Table B.10.1: Gabon: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 1.01 0.89 0.76 

Std. dev. (0.97) (0.89) (0.81) 

 N 762 1,500 2,054 

20-24 Mean 1.39 1.31 1.02 

Std. dev. (1.04) (1.03) (1.20) 

 N 762 1,500 2,054 

25-29 Mean 1.33 1.09 0.96 

Std. dev. (1.05) (1.01) (1.42) 

 N 762 1,500 916 

30-34 Mean 1.13 0.87 

Std. dev. (1.06) (1.11) 

 N 762 1,500 

35-39 Mean 0.79 0.58 

Std. dev. (1.00) (1.16) 

 N 762 656 

40-44 Mean 0.32 

Std. dev. (0.89) 

 N 762 

45-49 Mean 0.03 

Std. dev. (0.29) 

 N 269 
63 

Table B.10.2: Gabon: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

 to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

 to 

1970-1979 Average 

15-19 Difference in means -0.12 -0.13 -0.13 

Ratio of means 0.88 0.85 0.87 

 

T-statistic for difference 

between means (2.80) (4.56) 

20-24 Difference in means -0.08 -0.29 -0.18 

Ratio of means 0.94 0.78 0.86 

 

T-statistic for difference 

between means (1.77) (7.61) 

25-29 Difference in means -0.24 -0.13 -0.18 

Ratio of means 0.82 0.88 0.85 

 

T-statistic for difference 

between means (5.10) (2.37) 

30-34 Difference in means -0.26 -0.26 

Ratio of means 0.77 0.77 

 

T-statistic for difference 

between means (5.42) 

35-39 Difference in means -0.21 -0.21 

Ratio of means 0.73 0.73 

 

T-statistic for difference 

between means (3.64) 

40-44 Difference in means 

Ratio of means 

 

T-statistic for difference 

between means 

45-49 Difference in means 

Ratio of means 

 

T-statistic for difference 

between means 

 Average of means -0.18 -0.18 

Average ratio 0.83 0.84 
64 

B.11 Ghana 

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.11.1: Ghana: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.11.2: Ghana: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
65 

Table B.11.1: Ghana: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.73 0.62 0.54 0.40 

Std. dev. (0.88) (0.78) (0.72) (0.67) 

 N 1,218 3,830 6,075 5,483 

20-24 Mean 1.41 1.29 1.21 0.98 

Std. dev. (0.96) (0.90) (0.97) (1.10) 

 N 1,218 3,830 5,695 3,672 

25-29 Mean 1.46 1.37 1.23 1.03 

Std. dev. (0.91) (0.88) (1.13) (1.29) 

 N 1,218 3,830 4,361 1,859 

30-34 Mean 1.36 1.22 1.01 0.95 

Std. dev. (0.91) (1.09) (1.13) (1.56) 

 N 1,218 3,482 2,671 420 

35-39 Mean 1.07 0.90 0.77 

Std. dev. (0.93) (1.14) (1.26) 

 N 1,218 2,524 1,347 

40-44 Mean 0.63 0.45 0.56 

Std. dev. (0.99) (0.89) (1.26) 

 N 1,027 1,417 291 

45-49 Mean 0.20 0.18 

Std. dev. (0.73) (0.72) 

 N 510 570 
66 

Table B.11.2: Ghana: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

 to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.10 -0.08 -0.14 -0.11 

Ratio of means 0.86 0.87 0.73 0.82 

 T-statistic for difference between means (3.64) (5.26) (11.11) 

20-24 Difference in means -0.13 -0.08 -0.23 -0.14 

Ratio of means 0.91 0.94 0.81 0.89 

 T-statistic for difference between means (4.03) (3.95) (10.31) 

25-29 Difference in means -0.09 -0.14 -0.21 -0.15 

Ratio of means 0.94 0.90 0.83 0.89 

 T-statistic for difference between means (3.15) (6.13) (6.01) 

30-34 Difference in means -0.14 -0.21 -0.05 -0.14 

Ratio of means 0.90 0.83 0.95 0.89 

 T-statistic for difference between means (4.34) (7.44) (0.67) 

35-39 Difference in means -0.18 -0.12 -0.15 

Ratio of means 0.84 0.86 0.85 

 T-statistic for difference between means (5.03) (2.97) 

40-44 Difference in means -0.18 0.10 -0.04 

Ratio of means 0.72 1.23 0.97 

 T-statistic for difference between means (4.56) (1.35) 

45-49 Difference in means -0.02 -0.02 

Ratio of means 0.91 0.91 

 T-statistic for difference between means (0.38) 

 Average of means -0.12 -0.09 -0.16 

Average ratio 0.87 0.94 0.83 
67 

B.12 Guinea

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.12.1: Guinea: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.12.2: Guinea: Age-specific fertiliy rates, by mother's birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
68 

Table B.12.1: Guinea: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.85 0.81 0.87 

Std. dev. (0.92) (0.89) (0.85) 

 N 1,759 3,743 4,790 

20-24 Mean 1.35 1.39 1.37 

Std. dev. (0.93) (0.90) (1.01) 

 N 1,759 3,743 4,403 

25-29 Mean 1.43 1.49 1.32 

Std. dev. (0.94) (0.89) (1.26) 

 N 1,759 3,743 3,203 

30-34 Mean 1.32 1.32 1.10 

Std. dev. (0.92) (1.06) (1.24) 

 N 1,759 3,337 995 

35-39 Mean 0.98 0.94 

Std. dev. (0.93) (1.27) 

 N 1,759 2,325 

40-44 Mean 0.55 0.48 

Std. dev. (0.88) (1.02) 

 N 1,482 681 

45-49 Mean 0.17 

Std. dev. (0.64) 

 N 917 
69 

Table B.12.2: Guinea: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

 to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.04 0.05 0.01 

Ratio of means 0.96 1.07 1.01 

 T-statistic for difference between means (1.43) (2.85) 

20-24 Difference in means 0.04 -0.01 0.01 

Ratio of means 1.03 0.99 1.01 

 T-statistic for difference between means (1.52) (0.67) 

25-29 Difference in means 0.07 -0.17 -0.05 

Ratio of means 1.05 0.89 0.97 

 T-statistic for difference between means (2.49) (6.28) 

30-34 Difference in means 0.00 -0.23 -0.11 

Ratio of means 1.00 0.83 0.92 

 T-statistic for difference between means (0.09) (5.23) 

35-39 Difference in means -0.04 -0.04 

Ratio of means 0.96 0.96 

 T-statistic for difference between means (1.15) 

40-44 Difference in means -0.07 -0.07 

Ratio of means 0.88 0.88 

 T-statistic for difference between means (1.51) 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means -0.01 -0.09 

Average ratio 0.98 0.94 
70 

B.13 Kenya

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.13.1: Kenya: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.13.2: Kenya: Age-specific fertiliy rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
71 

Table B.13.1: Kenya: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.90 0.89 0.74 0.45 

Std. dev. (0.97) (0.92) (0.84) (0.73) 

 N 1,957 5,416 9,207 9,698 

20-24 Mean 1.62 1.67 1.53 1.25 

Std. dev. (1.04) (1.00) (1.08) (1.23) 

 N 1,957 5,416 8,803 5,817 

25-29 Mean 1.69 1.61 1.38 1.21 

Std. dev. (0.99) (0.98) (1.18) (1.41) 

 N 1,957 5,416 6,811 2,682 

30-34 Mean 1.51 1.28 1.02 1.12 

Std. dev. (1.06) (1.10) (1.18) (1.72) 

 N 1,957 5,093 3,821 620 

35-39 Mean 1.15 0.84 0.75 

Std. dev. (1.03) (1.15) (1.28) 

 N 1,957 3,723 1,814 

40-44 Mean 0.60 0.39 0.39 

Std. dev. (1.01) (0.88) (1.10) 

 N 1,746 1,909 442 

45-49 Mean 0.21 0.12 

Std. dev. (0.79) (0.61) 

 N 863 711 
72 

Table B.13.2: Kenya: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

 to 

 1970-1979 Average 

15-19 Difference in means 0.00 -0.15 -0.29 -0.15 

Ratio of means 1.00 0.83 0.61 0.81 

 T-statistic for difference between means (0.08) (9.93) (25.03) 

20-24 Difference in means 0.05 -0.14 -0.28 -0.12 

Ratio of means 1.03 0.91 0.82 0.92 

 T-statistic for difference between means (1.86) (8.02) (14.18) 

25-29 Difference in means -0.08 -0.22 -0.17 -0.16 

Ratio of means 0.95 0.86 0.88 0.90 

 T-statistic for difference between means (3.16) (11.36) (5.55) 

30-34 Difference in means -0.24 -0.26 0.10 -0.13 

Ratio of means 0.84 0.80 1.10 0.91 

 T-statistic for difference between means (8.35) (10.60) (1.42) 

35-39 Difference in means -0.31 -0.09 -0.20 

Ratio of means 0.73 0.90 0.81 

 T-statistic for difference between means (10.25) (2.41) 

40-44 Difference in means -0.21 0.01 -0.10 

Ratio of means 0.65 1.02 0.83 

 T-statistic for difference between means (6.69) (0.11) 

45-49 Difference in means -0.09 -0.09 

Ratio of means 0.56 0.56 

 T-statistic for difference between means (2.60) 

 Average of means -0.13 -0.14 -0.16 

Average ratio 0.82 0.89 0.85 
73 

B.14 Lesotho

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.14.1: Lesotho: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.14.2: Lesotho: Age-specific fertiliy rates, by mother's birth cohort

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
74 

Table B.14.1: Lesotho: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.47 0.43 0.41 

Std. dev. (0.62) (0.63) (0.59) 

 N 592 1,455 1,847 

20-24 Mean 1.38 1.19 1.00 

Std. dev. (0.82) (0.82) (0.81) 

 N 592 1,455 1,847 

25-29 Mean 1.23 1.04 0.82 

Std. dev. (0.81) (0.82) (1.05) 

 N 592 1,455 1,620 

30-34 Mean 1.00 0.76 0.68 

Std. dev. (0.83) (0.78) (1.16) 

 N 592 1,455 668 

35-39 Mean 0.69 0.57 

Std. dev. (0.78) (0.94) 

 N 592 1,329 

40-44 Mean 0.29 0.33 

Std. dev. (0.58) (0.93) 

 N 592 586 

45-49 Mean 0.11 

Std. dev. (0.53) 

 N 475 
75 

Table B.14.2: Lesotho: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

 to 

 1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.04 -0.03 -0.03 

Ratio of means 0.92 0.94 0.93 

 T-statistic for difference between means (1.21) (1.21) 

20-24 Difference in means -0.18 -0.19 -0.19 

Ratio of means 0.87 0.84 0.85 

 T-statistic for difference between means (4.63) (6.58) 

25-29 Difference in means -0.19 -0.22 -0.20 

Ratio of means 0.84 0.79 0.82 

 T-statistic for difference between means (4.83) (6.48) 

30-34 Difference in means -0.24 -0.08 -0.16 

Ratio of means 0.76 0.89 0.83 

 T-statistic for difference between means (5.95) (1.71) 

35-39 Difference in means -0.12 -0.12 

Ratio of means 0.82 0.82 

 T-statistic for difference between means (2.99) 

40-44 Difference in means 0.03 0.03 

Ratio of means 1.11 1.11 

 T-statistic for difference between means (0.73) 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means -0.12 -0.13 

Average ratio 0.89 0.87 
76 

B.15 Liberia

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.15.1: Liberia: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.15.2: Liberia: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969
77 

Table B.15.1: Liberia: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.82 0.81 0.78 

Std. dev. (0.99) (0.96) (0.89) 

 N 908 1,652 2,109 

20-24 Mean 1.28 1.40 1.41 

Std. dev. (1.15) (1.06) (1.47) 

 N 908 1,652 1,173 

25-29 Mean 1.41 1.40 

Std. dev. (1.10) (1.12) 

 N 908 1,652 

30-34 Mean 1.24 1.28 

Std. dev. (1.06) (1.53) 

 N 908 810 

35-39 Mean 0.93 

Std. dev. (1.07) 

 N 908 

40-44 Mean 0.65 

Std. dev. (1.40) 

 N 448 

45-49 Mean 

Std. dev. 

 N 
78 

Table B.15.2: Liberia: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.01 -0.03 -0.02 

Ratio of means 0.98 0.96 0.97 

 T-statistic for difference between means (0.33) (0.96) 

20-24 Difference in means 0.12 0.00 0.06 

Ratio of means 1.09 1.00 1.05 

 T-statistic for difference between means (2.56) (0.06) 

25-29 Difference in means -0.01 -0.01 

Ratio of means 0.99 0.99 

 T-statistic for difference between means (0.20) 

30-34 Difference in means 0.05 0.05 

Ratio of means 1.04 1.04 

 T-statistic for difference between means (0.71) 

35-39 Difference in means 

Ratio of means 

 T-statistic for difference between means 

40-44 Difference in means 

Ratio of means 

 T-statistic for difference between means 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means 0.04 -0.01 

Average ratio 1.03 0.98 
79 

B.16 Madagascar

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.16.1: Madagascar: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.16.2: Madagascar: Age-specific fertiliy rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
80 

Table B.16.1: Madagascar: Age-specific fertility rates by mother's age 

group and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.94 0.83 0.72 0.62 

Std. dev. (1.06) (0.99) (0.93) (0.88) 

 N 691 3,517 5,967 7,268 

20-24 Mean 1.55 1.49 1.33 1.31 

Std. dev. (1.17) (1.15) (1.08) (1.25) 

 N 691 3,517 5,967 4,597 

25-29 Mean 1.55 1.44 1.37 1.20 

Std. dev. (1.19) (1.08) (1.17) (1.34) 

 N 691 3,517 5,189 2,414 

30-34 Mean 1.35 1.23 1.15 1.01 

Std. dev. (1.15) (1.07) (1.28) (1.47) 

 N 691 3,517 3,301 742 

35-39 Mean 1.04 0.92 0.76 

Std. dev. (1.10) (1.14) (1.20) 

 N 691 2,963 1,748 

40-44 Mean 0.53 0.52 0.56 

Std. dev. (0.83) (1.07) (1.28) 

 N 691 1,661 584 

45-49 Mean 0.16 0.14 

Std. dev. (0.70) (0.70) 

 N 422 666 
81 

Table B.16.2: Madagascar: Differences in age-specific fertility rates between mothers' birth cohorts

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.11 -0.12 -0.10 -0.11 

Ratio of means 0.88 0.86 0.87 0.87 

 T-statistic for difference between means (2.53) (5.70) (6.05) 

20-24 Difference in means -0.06 -0.16 -0.03 -0.08 

Ratio of means 0.96 0.89 0.98 0.94 

 T-statistic for difference between means (1.30) (6.65) (1.12) 

25-29 Difference in means -0.11 -0.08 -0.17 -0.12 

Ratio of means 0.93 0.95 0.88 0.92 

 T-statistic for difference between means (2.18) (3.16) (5.36) 

30-34 Difference in means -0.12 -0.07 -0.15 -0.11 

Ratio of means 0.91 0.94 0.87 0.91 

 T-statistic for difference between means (2.57) (2.59) (2.49) 

35-39 Difference in means -0.12 -0.15 -0.14 

Ratio of means 0.88 0.83 0.86 

 T-statistic for difference between means (2.62) (4.35) 

40-44 Difference in means 0.00 0.03 0.01 

Ratio of means 0.99 1.06 1.03 

 T-statistic for difference between means (0.07) (0.55) 

45-49 Difference in means -0.02 -0.02 

Ratio of means 0.87 0.87 

 T-statistic for difference between means (0.47) 

 Average of means -0.08 -0.09 -0.11 

Average ratio 0.92 0.92 0.90 
82 

B.17 Malawi

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.17.1: Malawi: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.17.2: Malawi: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
83 

Table B.17.1: Malawi: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.77 0.85 0.88 0.72 

Std. dev. (1.01) (0.92) (0.88) (0.82) 

 N 504 3,280 6,562 10,249 

20-24 Mean 1.40 1.54 1.52 1.49 

Std. dev. (1.05) (0.99) (0.96) (1.16) 

 N 504 3,280 6,562 8,823 

25-29 Mean 1.56 1.54 1.43 1.34 

Std. dev. (1.03) (0.99) (1.03) (1.34) 

 N 504 3,280 5,886 5,070 

30-34 Mean 1.43 1.33 1.21 1.18 

Std. dev. (1.08) (1.00) (1.14) (1.49) 

 N 504 3,280 4,830 1,016 

35-39 Mean 1.19 1.02 0.89 

Std. dev. (1.03) (1.06) (1.29) 

 N 504 2,851 2,963 

40-44 Mean 0.68 0.61 0.53 

Std. dev. (0.90) (1.04) (1.15) 

 N 504 2,236 607 

45-49 Mean 0.43 0.26 

Std. dev. (1.22) (0.80) 

 N 250 1,125 
84 

Table B.17.2: Malawi: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.08 0.03 -0.16 -0.02 

Ratio of means 1.10 1.03 0.82 0.99 

 T-statistic for difference between means (1.67) (1.44) (11.56) 

20-24 Difference in means 0.14 -0.02 -0.03 0.03 

Ratio of means 1.10 0.98 0.98 1.02 

 T-statistic for difference between means (2.79) (1.11) (1.89) 

25-29 Difference in means -0.02 -0.11 -0.09 -0.07 

Ratio of means 0.98 0.93 0.94 0.95 

 T-statistic for difference between means (0.51) (4.90) (3.87) 

30-34 Difference in means -0.10 -0.12 -0.03 -0.08 

Ratio of means 0.93 0.91 0.98 0.94 

 T-statistic for difference between means (1.94) (5.02) (0.57) 

35-39 Difference in means -0.16 -0.13 -0.15 

Ratio of means 0.86 0.87 0.87 

 T-statistic for difference between means (3.22) (4.22) 

40-44 Difference in means -0.07 -0.08 -0.07 

Ratio of means 0.90 0.87 0.89 

 T-statistic for difference between means (1.53) (1.51) 

45-49 Difference in means -0.17 -0.17 

Ratio of means 0.60 0.60 

 T-statistic for difference between means (2.14) 

 Average of means -0.04 -0.07 -0.08 

Average ratio 0.93 0.93 0.93 
85 

B.18 Mali 

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.18.1: Mali: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.18.2: Mali: Age-specific fertiliy rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
86 

Table B.18.1: Mali: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.91 0.85 0.86 0.93 

Std. dev. (1.02) (0.98) (0.96) (0.98) 

 N 958 5,650 10,700 12,581 

20-24 Mean 1.48 1.58 1.56 1.59 

Std. dev. (1.13) (1.05) (1.09) (1.04) 

 N 958 5,650 10,220 11,569 

25-29 Mean 1.53 1.64 1.68 1.56 

Std. dev. (1.10) (1.01) (1.06) (1.14) 

 N 958 5,650 9,493 9,932 

30-34 Mean 1.46 1.50 1.47 1.34 

Std. dev. (1.14) (1.20) (1.08) (1.47) 

 N 958 5,113 8,469 4,639 

35-39 Mean 1.15 1.21 1.08 1.05 

Std. dev. (1.09) (1.15) (1.13) (2.04) 

 N 958 4,180 7,032 788 

40-44 Mean 0.68 0.66 0.61 

Std. dev. (1.16) (0.98) (1.19) 

 N 648 3,255 3,308 

45-49 Mean 0.21 0.20 0.24 

Std. dev. (0.81) (0.75) (1.11) 

 N 360 2,140 730 
87 

Table B.18.2: Mali: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.06 0.01 0.07 0.01 

Ratio of means 0.93 1.02 1.08 1.01 

 T-statistic for difference between means (1.67) (0.87) (5.60) 

20-24 Difference in means 0.11 -0.02 0.02 0.04 

Ratio of means 1.07 0.99 1.02 1.03 

 T-statistic for difference between means (2.78) (1.09) (1.69) 

25-29 Difference in means 0.11 0.04 -0.12 0.01 

Ratio of means 1.07 1.02 0.93 1.01 

 T-statistic for difference between means (2.98) (2.13) (7.75) 

30-34 Difference in means 0.04 -0.03 -0.13 -0.04 

Ratio of means 1.03 0.98 0.91 0.97 

 T-statistic for difference between means (0.93) (1.48) (5.17) 

35-39 Difference in means 0.07 -0.13 -0.03 -0.03 

Ratio of means 1.06 0.89 0.97 0.97 

 T-statistic for difference between means (1.74) (5.88) (0.41) 

40-44 Difference in means -0.02 -0.05 -0.03 

Ratio of means 0.97 0.93 0.95 

 T-statistic for difference between means (0.44) (1.71) 

45-49 Difference in means -0.02 0.05 0.02 

Ratio of means 0.92 1.25 1.08 

 T-statistic for difference between means (0.39) (1.09) 

 Average of means 0.03 -0.02 -0.04 

Average ratio 1.01 1.01 0.98 
88 

 B.19 Mozambique

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.19.1: Mozambique: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.19.2: Mozambique: Age-specific fertility rates, 

by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
89 

Table B.19.1: Mozambique: Age-specific fertility rates by mother's age 

group and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.85 0.87 0.83 0.81 

Std. dev. (1.03) (1.01) (0.94) (0.86) 

 N 272 2,582 5,222 7,435 

20-24 Mean 1.19 1.29 1.37 1.32 

Std. dev. (1.07) (1.03) (0.96) (1.08) 

 N 272 2,582 5,222 6,029 

25-29 Mean 1.28 1.33 1.28 1.23 

Std. dev. (1.13) (0.99) (0.96) (1.40) 

 N 272 2,582 5,222 3,353 

30-34 Mean 1.10 1.19 1.03 1.07 

Std. dev. (0.99) (1.07) (1.07) (1.46) 

 N 272 2,582 4,103 773 

35-39 Mean 0.76 0.85 0.86 

Std. dev. (0.94) (0.97) (1.31) 

 N 272 2,582 2,247 

40-44 Mean 0.43 0.52 0.45 

Std. dev. (0.72) (0.88) (1.08) 

 N 272 1,849 561 

45-49 Mean 0.09 0.22 

Std. dev. (0.35) (0.74) 

 N 272 832 
90 

Table B.19.2: Mozambique: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.03 -0.05 -0.02 -0.01 

Ratio of means 1.03 0.95 0.98 0.99 

 T-statistic for difference between means (0.40) (1.94) (0.95) 

20-24 Difference in means 0.11 0.08 -0.05 0.04 

Ratio of means 1.09 1.06 0.96 1.04 

 T-statistic for difference between means (1.54) (3.44) (2.80) 

25-29 Difference in means 0.05 -0.05 -0.05 -0.02 

Ratio of means 1.04 0.97 0.96 0.99 

 T-statistic for difference between means (0.70) (1.96) (1.84) 

30-34 Difference in means 0.09 -0.16 0.04 -0.01 

Ratio of means 1.08 0.87 1.04 1.00 

 T-statistic for difference between means (1.40) (5.93) (0.76) 

35-39 Difference in means 0.09 0.01 0.05 

Ratio of means 1.12 1.02 1.07 

 T-statistic for difference between means (1.50) (0.39) 

40-44 Difference in means 0.09 -0.07 0.01 

Ratio of means 1.21 0.87 1.04 

 T-statistic for difference between means (1.85) (1.32) 

45-49 Difference in means 0.13 0.13 

Ratio of means 2.55 2.55 

 T-statistic for difference between means (3.97) 

 Average of means 0.08 -0.04 -0.02 

Average ratio 1.30 0.96 0.99 
91 

B.20 Namibia

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.20.1: Namibia: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.20.2: Namibia: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979
92 

Table B.20.1: Namibia: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.43 0.47 0.44 0.34 

Std. dev. (0.76) (0.73) (0.69) (0.61) 

 N 555 2,063 3,554 4,051 

20-24 Mean 1.20 1.18 1.01 0.86 

Std. dev. (1.05) (0.99) (0.92) (1.17) 

 N 555 2,063 3,554 2,666 

25-29 Mean 1.42 1.25 1.08 0.85 

Std. dev. (1.02) (0.96) (1.10) (1.20) 

 N 555 2,063 2,871 963 

30-34 Mean 1.23 1.07 0.96 

Std. dev. (1.05) (0.96) (1.28) 

 N 555 2,063 1,874 

35-39 Mean 0.98 0.85 0.70 

Std. dev. (1.01) (1.08) (1.13) 

 N 555 1,616 708 

40-44 Mean 0.53 0.54 

Std. dev. (0.80) (1.12) 

 N 555 996 

45-49 Mean 0.23 0.15 

Std. dev. (0.79) (0.67) 

 N 283 292 
93 

Table B.20.2: Namibia: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.04 -0.03 -0.10 -0.03 

Ratio of means 1.09 0.94 0.77 0.93 

 T-statistic for difference between means (1.07) (1.33) (6.87) 

20-24 Difference in means -0.02 -0.17 -0.15 -0.11 

Ratio of means 0.99 0.86 0.85 0.90 

 T-statistic for difference between means (0.36) (6.39) (5.52) 

25-29 Difference in means -0.17 -0.17 -0.23 -0.19 

Ratio of means 0.88 0.86 0.79 0.84 

 T-statistic for difference between means (3.54) (5.82) (5.21) 

30-34 Difference in means -0.16 -0.11 -0.13 

Ratio of means 0.87 0.90 0.88 

 T-statistic for difference between means (3.20) (3.06) 

35-39 Difference in means -0.14 -0.14 -0.14 

Ratio of means 0.86 0.83 0.85 

 T-statistic for difference between means (2.71) (2.83) 

40-44 Difference in means 0.01 0.01 

Ratio of means 1.02 1.02 

 T-statistic for difference between means (0.24) 

45-49 Difference in means -0.08 -0.08 

Ratio of means 0.65 0.65 

 T-statistic for difference between means (1.31) 

 Average of means -0.07 -0.12 -0.16 

Average ratio 0.91 0.88 0.80 
94 

B.21 Niger

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.21.1: Niger: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.21.2: Niger: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
95 

Table B.21.1: Niger: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.97 1.05 1.17 0.97 

Std. dev. (1.02) (1.00) (1.00) (0.99) 

 N 646 2,906 6,367 7,518 

20-24 Mean 1.57 1.62 1.72 1.68 

Std. dev. (1.07) (0.98) (0.97) (1.33) 

 N 646 2,906 6,367 5,180 

25-29 Mean 1.67 1.71 1.68 1.59 

Std. dev. (1.04) (1.01) (1.18) (1.27) 

 N 646 2,906 5,557 3,230 

30-34 Mean 1.58 1.47 1.52 1.41 

Std. dev. (1.03) (1.01) (1.40) (1.41) 

 N 646 2,906 3,706 1,236 

35-39 Mean 1.30 1.11 1.20 

Std. dev. (1.04) (1.18) (1.27) 

 N 646 2,421 2,083 

40-44 Mean 0.68 0.62 0.68 

Std. dev. (0.88) (1.24) (1.20) 

 N 646 1,346 778 

45-49 Mean 0.19 0.24 

Std. dev. (0.67) (0.85) 

 N 422 488 
96 

Table B.21.2: Niger: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.08 0.12 -0.20 0.00 

Ratio of means 1.09 1.11 0.83 1.01 

 T-statistic for difference between means (1.92) (5.20) (11.72) 

20-24 Difference in means 0.05 0.09 -0.03 0.04 

Ratio of means 1.03 1.06 0.98 1.02 

 T-statistic for difference between means (1.10) (4.25) (1.50) 

25-29 Difference in means 0.04 -0.03 -0.09 -0.03 

Ratio of means 1.02 0.98 0.95 0.98 

 T-statistic for difference between means (0.85) (1.20) (3.32) 

30-34 Difference in means -0.10 0.05 -0.11 -0.06 

Ratio of means 0.93 1.03 0.93 0.96 

 T-statistic for difference between means (2.34) (1.63) (2.37) 

35-39 Difference in means -0.19 0.09 -0.05 

Ratio of means 0.85 1.08 0.97 

 T-statistic for difference between means (4.02) (2.47) 

40-44 Difference in means -0.07 0.06 0.00 

Ratio of means 0.90 1.10 1.00 

 T-statistic for difference between means (1.35) (1.09) 

45-49 Difference in means 0.05 0.05 

Ratio of means 1.27 1.27 

 T-statistic for difference between means (1.02) 

 Average of means -0.02 0.06 -0.11 

Average ratio 1.02 1.06 0.92 
97 

B.22 Nigeria

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.22.1: Nigeria: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.22.2: Nigeria: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
98 

Table B.22.1: Nigeria: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.76 0.82 0.81 0.63 

Std. dev. (0.99) (1.00) (0.97) (0.92) 

 N 1,107 4,085 7,136 7,442 

20-24 Mean 1.37 1.38 1.38 1.21 

Std. dev. (1.09) (1.06) (1.13) (1.15) 

 N 1,107 4,085 7,136 5,146 

25-29 Mean 1.47 1.55 1.42 1.34 

Std. dev. (1.04) (1.01) (1.14) (1.50) 

 N 1,107 4,085 5,455 3,196 

30-34 Mean 1.42 1.30 1.25 1.43 

Std. dev. (1.04) (1.14) (1.18) (2.00) 

 N 1,107 4,085 3,378 644 

35-39 Mean 1.13 0.90 0.93 

Std. dev. (1.03) (1.11) (1.36) 

 N 1,107 2,945 2,068 

40-44 Mean 0.57 0.45 0.54 

Std. dev. (1.08) (0.94) (1.35) 

 N 1,107 1,746 499 

45-49 Mean 0.31 0.18 

Std. dev. (0.99) (0.76) 

 N 412 917 
99 

Table B.22.2: Nigeria: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

 to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

 to 

1970-1979 Average 

15-19 Difference in means 0.06 -0.01 -0.18 -0.04 

Ratio of means 1.08 0.99 0.78 0.95 

 T-statistic for difference between means (1.87) (0.38) (11.52) 

20-24 Difference in means 0.01 0.00 -0.17 -0.05 

Ratio of means 1.01 1.00 0.88 0.96 

 T-statistic for difference between means (0.35) (0.17) (8.27) 

25-29 Difference in means 0.08 -0.13 -0.08 -0.04 

Ratio of means 1.06 0.91 0.94 0.97 

 T-statistic for difference between means (2.32) (5.97) (2.73) 

30-34 Difference in means -0.13 -0.04 0.17 0.00 

Ratio of means 0.91 0.97 1.14 1.00 

 T-statistic for difference between means (3.59) (1.54) (2.12) 

35-39 Difference in means -0.23 0.03 -0.10 

Ratio of means 0.79 1.04 0.92 

 T-statistic for difference between means (6.25) (0.92) 

40-44 Difference in means -0.12 0.08 -0.02 

Ratio of means 0.80 1.19 0.99 

 T-statistic for difference between means (2.94) (1.31) 

45-49 Difference in means -0.14 -0.14 

Ratio of means 0.56 0.56 

 T-statistic for difference between means (2.55) 

 Average of means -0.07 -0.01 -0.07 

Average ratio 0.89 1.02 0.93 
100 

B.23 Rwanda

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.23.1: Rwanda: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.23.2: Rwanda: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
101 

Table B.23.1: Rwanda: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.51 0.33 0.29 0.24 

Std. dev. (0.76) (0.64) (0.60) (0.54) 

 N 598 3,626 6,751 8,481 

20-24 Mean 1.53 1.38 1.25 1.10 

Std. dev. (0.98) (0.98) (1.00) (1.14) 

 N 598 3,626 6,751 6,465 

25-29 Mean 1.86 1.79 1.59 1.43 

Std. dev. (0.94) (0.92) (1.07) (1.33) 

 N 598 3,626 5,796 4,060 

30-34 Mean 1.78 1.63 1.41 1.42 

Std. dev. (0.98) (0.94) (1.22) (1.42) 

 N 598 3,626 4,337 1,156 

35-39 Mean 1.47 1.23 1.11 

Std. dev. (0.96) (1.05) (1.22) 

 N 598 2,876 2,770 

40-44 Mean 0.82 0.73 0.76 

Std. dev. (0.86) (1.10) (1.25) 

 N 598 1,999 863 

45-49 Mean 0.28 0.22 

Std. dev. (0.83) (0.79) 

 N 278 1,006 
102 

Table B.23.2: Rwanda: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

 to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.18 -0.03 -0.05 -0.09 

Ratio of means 0.65 0.90 0.83 0.79 

 T-statistic for difference between means (5.51) (2.60) (5.36) 

20-24 Difference in means -0.15 -0.13 -0.15 -0.14 

Ratio of means 0.90 0.91 0.88 0.90 

 T-statistic for difference between means (3.56) (6.35) (7.83) 

25-29 Difference in means -0.07 -0.20 -0.15 -0.14 

Ratio of means 0.96 0.89 0.90 0.92 

 T-statistic for difference between means (1.65) (9.69) (6.09) 

30-34 Difference in means -0.15 -0.22 0.01 -0.12 

Ratio of means 0.91 0.86 1.01 0.93 

 T-statistic for difference between means (3.52) (9.11) (0.26) 

35-39 Difference in means -0.24 -0.11 -0.18 

Ratio of means 0.84 0.91 0.87 

 T-statistic for difference between means (5.50) (3.75) 

40-44 Difference in means -0.10 0.03 -0.03 

Ratio of means 0.88 1.05 0.97 

 T-statistic for difference between means (2.22) (0.68) 

45-49 Difference in means -0.06 -0.06 

Ratio of means 0.79 0.79 

 T-statistic for difference between means (1.05) 

 Average of means -0.14 -0.11 -0.08 

Average ratio 0.85 0.92 0.91 
103 

B.24 Senegal

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.24.1: Senegal: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.24.2: Senegal: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
104 

Table B.24.1: Senegal: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.87 0.79 0.71 0.50 

Std. dev. (0.94) (0.89) (0.88) (0.79) 

 N 1,095 5,185 9,605 11,169 

20-24 Mean 1.51 1.49 1.34 1.06 

Std. dev. (0.97) (0.96) (1.06) (1.14) 

 N 1,095 5,185 8,230 7,937 

25-29 Mean 1.62 1.55 1.40 1.28 

Std. dev. (0.96) (0.97) (1.08) (1.54) 

 N 1,095 5,185 6,764 3,968 

30-34 Mean 1.48 1.46 1.22 1.19 

Std. dev. (0.97) (1.10) (1.17) (1.50) 

 N 1,095 4,246 4,769 1,128 

35-39 Mean 1.17 1.10 0.99 

Std. dev. (1.01) (1.04) (1.43) 

 N 1,095 3,361 2,447 

40-44 Mean 0.70 0.62 0.54 

Std. dev. (0.97) (1.08) (1.16) 

 N 745 2,048 618 

45-49 Mean 0.27 0.16 

Std. dev. (0.79) (0.73) 

 N 433 790 
105 

Table B.24.2: Senegal: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.08 -0.09 -0.20 -0.12 

Ratio of means 0.91 0.89 0.71 0.84 

 T-statistic for difference between means (2.43) (5.62) (17.24) 

20-24 Difference in means -0.02 -0.15 -0.28 -0.15 

Ratio of means 0.99 0.90 0.79 0.89 

 T-statistic for difference between means (0.56) (8.40) (16.03) 

25-29 Difference in means -0.07 -0.15 -0.12 -0.11 

Ratio of means 0.96 0.90 0.91 0.92 

 T-statistic for difference between means (2.03) (8.15) (4.46) 

30-34 Difference in means -0.02 -0.24 -0.03 -0.10 

Ratio of means 0.98 0.84 0.98 0.93 

 T-statistic for difference between means (0.69) (9.88) (0.63) 

35-39 Difference in means -0.07 -0.11 -0.09 

Ratio of means 0.94 0.90 0.92 

 T-statistic for difference between means (1.88) (3.34) 

40-44 Difference in means -0.08 -0.09 -0.08 

Ratio of means 0.89 0.86 0.88 

 T-statistic for difference between means (1.77) (1.63) 

45-49 Difference in means -0.11 -0.11 

Ratio of means 0.59 0.59 

 T-statistic for difference between means (2.36) 

 Average of means -0.06 -0.14 -0.16 

Average ratio 0.90 0.88 0.85 
106 

B.25 South Africa

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.25.1: South Africa: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.25.2: South Africa: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979
107 

Table B.25.1: South Africa: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.48 0.44 0.48 0.38 

Std. dev. (0.74) (0.67) (0.67) (0.57) 

 N 253 2,512 3,326 3,984 

20-24 Mean 1.19 0.98 0.88 0.71 

Std. dev. (1.08) (0.89) (0.81) (1.04) 

 N 253 2,512 3,326 3,139 

25-29 Mean 1.02 0.92 0.78 0.74 

Std. dev. (0.97) (0.85) (0.76) (1.41) 

 N 253 2,512 3,326 1,088 

30-34 Mean 0.70 0.70 0.61 

Std. dev. (0.81) (0.81) (0.95) 

 N 253 2,512 2,603 

35-39 Mean 0.61 0.44 0.43 

Std. dev. (0.80) (0.69) (1.14) 

 N 253 2,512 977 

40-44 Mean 0.22 0.22 

Std. dev. (0.53) (0.70) 

 N 253 1,880 

45-49 Mean 0.06 0.06 

Std. dev. (0.28) (0.40) 

 N 253 660 
108 

Table B.25.2: South Africa: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

 to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.04 0.03 -0.10 -0.04 

Ratio of means 0.92 1.07 0.79 0.93 

 T-statistic for difference between means (0.83) (1.88) (6.84) 

20-24 Difference in means -0.21 -0.10 -0.18 -0.16 

Ratio of means 0.83 0.90 0.80 0.84 

 T-statistic for difference between means (2.97) (4.48) (7.50) 

25-29 Difference in means -0.10 -0.14 -0.04 -0.09 

Ratio of means 0.90 0.84 0.95 0.90 

 T-statistic for difference between means (1.53) (6.71) (0.79) 

30-34 Difference in means 0.00 -0.09 -0.04 

Ratio of means 1.00 0.88 0.94 

 T-statistic for difference between means (0.00) (3.51) 

35-39 Difference in means -0.17 -0.01 -0.09 

Ratio of means 0.73 0.99 0.86 

 T-statistic for difference between means (3.17) (0.15) 

40-44 Difference in means 0.00 0.00 

Ratio of means 0.98 0.98 

 T-statistic for difference between means (0.12) 

45-49 Difference in means 0.00 0.00 

Ratio of means 0.95 0.95 

 T-statistic for difference between means (0.14) 

 Average of means -0.07 -0.06 -0.10 

Average ratio 0.90 0.94 0.85 
109 

B.26 Tanzania

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.26.1: Tanzania: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.26.2: Tanzania: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
110 

Table B.26.1: Tanzania: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.97 0.93 0.74 0.52 

Std. dev. (0.97) (0.92) (0.82) (0.74) 

 N 1,389 4,052 7,584 9,501 

20-24 Mean 1.51 1.54 1.42 1.30 

Std. dev. (1.02) (0.94) (0.94) (1.19) 

 N 1,389 4,052 7,584 5,714 

25-29 Mean 1.46 1.49 1.37 1.30 

Std. dev. (0.97) (0.95) (1.12) (1.39) 

 N 1,389 4,052 6,325 3,043 

30-34 Mean 1.40 1.30 1.14 1.15 

Std. dev. (1.02) (0.98) (1.22) (1.47) 

 N 1,389 4,052 3,461 1,088 

35-39 Mean 1.04 0.97 0.86 

Std. dev. (0.97) (1.12) (1.29) 

 N 1,389 3,374 1,738 

40-44 Mean 0.61 0.56 0.52 

Std. dev. (0.86) (1.06) (1.08) 

 N 1,389 1,706 591 

45-49 Mean 0.22 0.15 

Std. dev. (0.76) (0.69) 

 N 921 628 
111 

Table B.26.2: Tanzania: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

 1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.04 -0.19 -0.22 -0.15 

Ratio of means 0.96 0.80 0.70 0.82 

 T-statistic for difference between means (1.38) (10.99) (18.32) 

20-24 Difference in means 0.03 -0.11 -0.12 -0.07 

Ratio of means 1.02 0.93 0.91 0.95 

 T-statistic for difference between means (0.83) (6.24) (6.53) 

25-29 Difference in means 0.03 -0.12 -0.07 -0.05 

Ratio of means 1.02 0.92 0.95 0.96 

 T-statistic for difference between means (0.91) (5.81) (2.30) 

30-34 Difference in means -0.10 -0.15 0.01 -0.08 

Ratio of means 0.93 0.88 1.01 0.94 

 T-statistic for difference between means (3.23) (5.95) (0.20) 

35-39 Difference in means -0.07 -0.11 -0.09 

Ratio of means 0.93 0.89 0.91 

 T-statistic for difference between means (2.12) (2.93) 

40-44 Difference in means -0.04 -0.04 -0.04 

Ratio of means 0.93 0.93 0.93 

 T-statistic for difference between means (1.27) (0.80) 

45-49 Difference in means -0.07 -0.07 

Ratio of means 0.69 0.69 

 T-statistic for difference between means (1.86) 

 Average of means -0.04 -0.12 -0.10 

Average ratio 0.92 0.89 0.89 
112 

B.27 Togo

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.27.1: Togo: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.27.2: Togo: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979
113 

Table B.27.1: Togo: Age-specific fertility rates by mother's age group and 

birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.71 0.71 0.62 0.40 

Std. dev. (0.86) (0.84) (0.76) (0.69) 

 N 637 2,316 3,885 3,643 

20-24 Mean 1.41 1.40 1.30 1.06 

Std. dev. (0.94) (0.91) (1.06) (1.25) 

 N 637 2,316 3,402 2,137 

25-29 Mean 1.59 1.53 1.35 1.27 

Std. dev. (0.89) (0.92) (1.17) (1.65) 

 N 637 2,316 2,330 639 

30-34 Mean 1.43 1.37 1.15 

Std. dev. (0.89) (1.17) (1.31) 

 N 637 1,990 1,303 

35-39 Mean 1.16 1.09 0.90 

Std. dev. (0.92) (1.21) (1.67) 

 N 637 1,225 473 

40-44 Mean 0.75 0.58 

Std. dev. (1.10) (1.08) 

 N 487 692 

45-49 Mean 

Std. dev. 

 N 
114 

Table B.27.2: Togo: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.01 -0.09 -0.23 -0.10 

Ratio of means 1.01 0.87 0.63 0.84 

 T-statistic for difference between means (0.19) (4.24) (13.66) 

20-24 Difference in means 0.00 -0.10 -0.24 -0.11 

Ratio of means 1.00 0.93 0.82 0.91 

 T-statistic for difference between means (0.09) (3.90) (7.26) 

25-29 Difference in means -0.06 -0.18 -0.08 -0.11 

Ratio of means 0.96 0.89 0.94 0.93 

 T-statistic for difference between means (1.62) (5.70) (1.14) 

30-34 Difference in means -0.06 -0.22 -0.14 

Ratio of means 0.96 0.84 0.90 

 T-statistic for difference between means (1.40) (4.86) 

35-39 Difference in means -0.07 -0.19 -0.13 

Ratio of means 0.94 0.83 0.88 

 T-statistic for difference between means (1.44) (2.27) 

40-44 Difference in means -0.17 -0.17 

Ratio of means 0.77 0.77 

 T-statistic for difference between means (2.64) 

45-49 Difference in means 

Ratio of means 

 T-statistic for difference between means 

 Average of means -0.06 -0.16 -0.18 

Average ratio 0.94 0.87 0.80 
115 

B.28 Uganda

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.28.1: Uganda: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.28.2: Uganda: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
116 

Table B.28.1: Uganda: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 1.07 1.03 0.92 0.81 

Std. dev. (1.02) (0.98) (0.91) (0.96) 

 N 888 3,369 7,285 9,279 

20-24 Mean 1.69 1.65 1.61 1.68 

Std. dev. (1.08) (1.02) (1.10) (1.20) 

 N 888 3,369 6,694 6,437 

25-29 Mean 1.63 1.60 1.64 1.59 

Std. dev. (1.06) (1.03) (1.28) (1.24) 

 N 888 3,369 5,398 3,570 

30-34 Mean 1.48 1.41 1.39 1.44 

Std. dev. (1.04) (1.14) (1.24) (1.58) 

 N 888 2,962 3,512 1,285 

35-39 Mean 1.11 1.06 1.08 

Std. dev. (1.01) (1.18) (1.27) 

 N 888 2,270 1,968 

40-44 Mean 0.63 0.57 0.57 

Std. dev. (1.02) (1.08) (1.17) 

 N 736 1,289 686 

45-49 Mean 0.23 0.20 

Std. dev. (0.82) (0.71) 

 N 414 539 
117 

Table B.28.2: Uganda: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.04 -0.12 -0.10 -0.08 

Ratio of means 0.97 0.89 0.89 0.91 

 T-statistic for difference between means (0.94) (5.74) (7.03) 

20-24 Difference in means -0.04 -0.03 0.07 0.00 

Ratio of means 0.98 0.98 1.04 1.00 

 T-statistic for difference between means (0.90) (1.56) (3.37) 

25-29 Difference in means -0.03 0.05 -0.06 -0.01 

Ratio of means 0.98 1.03 0.97 0.99 

 T-statistic for difference between means (0.85) (1.96) (2.04) 

30-34 Difference in means -0.07 -0.02 0.04 -0.02 

Ratio of means 0.95 0.99 1.03 0.99 

 T-statistic for difference between means (1.70) (0.67) (0.89) 

35-39 Difference in means -0.05 0.02 -0.01 

Ratio of means 0.96 1.02 0.99 

 T-statistic for difference between means (1.07) (0.46) 

40-44 Difference in means -0.06 0.00 -0.03 

Ratio of means 0.91 1.00 0.95 

 T-statistic for difference between means (1.24) (0.04) 

45-49 Difference in means -0.02 -0.02 

Ratio of means 0.89 0.89 

 T-statistic for difference between means (0.49) 

 Average of means -0.04 -0.02 -0.01 

Average ratio 0.95 0.98 0.98 
118 

B.29 Zambia

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.29.1: Zambia: Cumulative number of births, 

by mother's age and birth cohort 

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.29.2: Zambia: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
119 

Table B.29.1: Zambia: Age-specific fertility rates by mother's age group 

and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 1.05 1.05 0.85 0.61 

Std. dev. (0.97) (0.92) (0.83) (0.77) 

 N 1,035 3,416 6,094 8,826 

20-24 Mean 1.73 1.68 1.47 1.38 

Std. dev. (0.97) (0.94) (0.96) (1.24) 

 N 1,035 3,416 6,094 5,167 

25-29 Mean 1.70 1.53 1.40 1.28 

Std. dev. (0.96) (0.94) (1.11) (1.49) 

 N 1,035 3,416 5,216 1,977 

30-34 Mean 1.50 1.31 1.27 1.30 

Std. dev. (0.96) (0.97) (1.33) (1.94) 

 N 1,035 3,416 3,032 337 

35-39 Mean 1.20 1.02 0.97 

Std. dev. (0.99) (1.13) (1.40) 

 N 1,035 2,841 1,118 

40-44 Mean 0.64 0.56 

Std. dev. (0.86) (1.03) 

 N 1,035 1,564 

45-49 Mean 0.18 0.15 

Std. dev. (0.61) (0.66) 

 N 678 515 
120 

Table B.29.2: Zambia: Differences in age-specific fertility rates between mothers' birth cohorts 

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means 0.00 -0.20 -0.24 -0.15 

Ratio of means 1.00 0.81 0.72 0.84 

 T-statistic for difference between means (0.04) (10.35) (17.98) 

20-24 Difference in means -0.05 -0.21 -0.08 -0.11 

Ratio of means 0.97 0.87 0.94 0.93 

 T-statistic for difference between means (1.43) (10.45) (3.97) 

25-29 Difference in means -0.17 -0.13 -0.12 -0.14 

Ratio of means 0.90 0.92 0.91 0.91 

 T-statistic for difference between means (4.92) (5.84) (3.32) 

30-34 Difference in means -0.19 -0.04 0.03 -0.07 

Ratio of means 0.88 0.97 1.02 0.96 

 T-statistic for difference between means (5.41) (1.42) (0.29) 

35-39 Difference in means -0.18 -0.04 -0.11 

Ratio of means 0.85 0.96 0.90 

 T-statistic for difference between means (4.80) (0.90) 

40-44 Difference in means -0.07 -0.07 

Ratio of means 0.89 0.89 

 T-statistic for difference between means (1.94) 

45-49 Difference in means -0.03 -0.03 

Ratio of means 0.86 0.86 

 T-statistic for difference between means (0.67) 

 Average of means -0.10 -0.12 -0.10 

Average ratio 0.91 0.91 0.90 
121 

B.30 Zimbabwe

0

1

2

3

4

5

6

7

8

9

0 15-19 20-24 25-29 30-34 35-39 40-44 45-49

Number of births

Age group

Figure B.30.1: Zimbabwe: Cumulative number of births, 

by mother's age and birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

15-19 20-24 25-29 30-34 35-39 40-44 45-49

Average number of births per woman in the age group

Age group

Figure B.30.2: Zimbabwe: Age-specific fertility rates, by mother's birth cohort

Cohort 1940-1949

Cohort 1950-1959

Cohort 1960-1969

Cohort 1970-1979

Cohort 1980-1989
122 

Table B.30.1: Zimbabwe: Age-specific fertility rates by mother's age 

group and birth cohort

Mother's Birth Cohort 

Age group 1940-1949 1950-1959 1960-1969 1970-1979 

15-19 Mean 0.75 0.67 0.62 0.41 

Std. dev. (0.91) (0.81) (0.76) (0.66) 

 N 1,050 3,584 6,241 7,907 

20-24 Mean 1.50 1.49 1.27 1.04 

Std. dev. (1.00) (0.94) (0.98) (1.07) 

 N 1,050 3,584 5,715 5,104 

25-29 Mean 1.51 1.43 1.09 0.98 

Std. dev. (0.99) (0.92) (1.02) (1.20) 

 N 1,050 3,584 4,387 2,724 

30-34 Mean 1.33 1.19 0.84 0.78 

Std. dev. (0.97) (1.02) (1.05) (1.24) 

 N 1,050 3,211 2,762 856 

35-39 Mean 0.97 0.77 0.57 

Std. dev. (0.96) (1.04) (1.02) 

 N 1,050 2,353 1,485 

40-44 Mean 0.50 0.37 0.35 

Std. dev. (0.93) (0.84) (0.98) 

 N 841 1,324 481 

45-49 Mean 0.18 0.15 

Std. dev. (0.77) (0.71) 

 N 449 542 
123 

Table B.30.2: Zimbabwe: Differences in age-specific fertility rates between mothers' birth cohorts

Mothers' Birth Cohort 

Age group 

1940-1949 

to 

1950-1959 

1950-1959 

to 

1960-1969 

1960-1969 

to 

1970-1979 Average 

15-19 Difference in means -0.08 -0.06 -0.21 -0.12 

Ratio of means 0.89 0.92 0.66 0.82 

 T-statistic for difference between means (2.63) (3.43) (17.01) 

20-24 Difference in means 0.00 -0.22 -0.23 -0.15 

Ratio of means 1.00 0.85 0.82 0.89 

 T-statistic for difference between means (0.07) (11.04) (11.37) 

25-29 Difference in means -0.08 -0.35 -0.11 -0.18 

Ratio of means 0.95 0.76 0.90 0.87 

 T-statistic for difference between means (2.26) (16.10) (3.95) 

30-34 Difference in means -0.14 -0.35 -0.06 -0.18 

Ratio of means 0.89 0.70 0.93 0.84 

 T-statistic for difference between means (4.04) (13.04) (1.25) 

35-39 Difference in means -0.20 -0.20 -0.20 

Ratio of means 0.80 0.74 0.77 

 T-statistic for difference between means (5.39) (5.79) 

40-44 Difference in means -0.14 -0.02 -0.08 

Ratio of means 0.73 0.95 0.84 

 T-statistic for difference between means (3.43) (0.35) 

45-49 Difference in means -0.03 -0.03 

Ratio of means 0.84 0.84 

 T-statistic for difference between means (0.62) 

 Average of means -0.09 -0.20 -0.15 

Average ratio 0.87 0.82 0.83 

 125 

Appendix C: Cohort/Age Group Statistics Suppressed Due to Small 

Sample Size

Table C.1: Values suppressed due to sample sizes under 250 

Country Age Group Mother's Birth Cohort Sample Size 

Benin 45-49 1960-1969 134 

Benin 35-39 1970-1979 227 

Burundi 45-49 1940-1949 114 

Burundi 35-39 1950-1959 180 

Chad 15-19 1940-1949 201 

Chad 20-24 1940-1949 201 

Chad 25-29 1940-1949 201 

Chad 30-34 1940-1949 201 

Chad 35-39 1940-1949 201 

Chad 40-44 1940-1949 201 

Chad 45-49 1940-1949 201 

Comoros 15-19 1940-1949 115 

Comoros 20-24 1940-1949 115 

Comoros 25-29 1940-1949 115 

Comoros 30-34 1940-1949 115 

Comoros 35-39 1940-1949 115 

Comoros 40-44 1940-1949 115 

Comoros 45-49 1940-1949 115 

Comoros 45-49 1950-1959 58 

Comoros 35-39 1960-1969 94 

Comoros 25-29 1970-1979 117 

Comoros 15-19 1980-1989 199 

Gabon 40-44 1960-1969 4 

Gabon 30-34 1970-1979 5 

Gabon 20-24 1980-1989 12 

Guinea 15-19 1940-1949 5 

Guinea 20-24 1940-1949 5 

Guinea 25-29 1940-1949 5 

Guinea 30-34 1940-1949 5 

Guinea 35-39 1940-1949 5 

Guinea 40-44 1940-1949 5 

Guinea 45-49 1940-1949 5 

(Cont’d)
 126 

Table C.1 – cont’d

Country Age Group Mother's Birth Cohort Sample Size 

Liberia 45-49 1940-1949 87 

Liberia 35-39 1950-1959 194 

Liberia 25-29 1960-1969 229 

Liberia 15-19 1970-1979 235 

Niger 45-49 1960-1969 163 

Niger 35-39 1970-1979 232 

Togo 45-49 1940-1949 220 

Togo 45-49 1950-1959 241 

Uganda 45-49 1960-1969 120 

Uganda 35-39 1970-1979 164 

Zambia 40-44 1960-1969 198 

Zimbabwe 45-49 1960-1969 17 

Zimbabwe 35-39 1970-1979 34 

Zimbabwe 25-29 1980-1989 45 
 

DHS Comparative Reports Series 

1. Westoff, Charles F. 2001. Unmet Need at the End of the Century.

2. Westoff, Charles F., and Akinrinola Bankole. 2002. Reproductive Preferences in Developing 

Countries at the Turn of the Century. 

3. Rutstein, Shea O. 2002. Fertility Levels, Trends, and Differentials 1995-1999.

4. Mahy, Mary. 2003. Childhood Mortality in the Developing World: A Review of Evidence from the 

Demographic and Health Surveys.

5. Westoff, Charles F. 2003. Trends in Marriage and Early Childbearing in Developing Countries.

6. Rutstein, Shea O., and Kiersten Johnson. 2004. The DHS Wealth Index.

7. Yoder, P. Stanley, Noureddine Abderrahim, and Arlinda Zhuzhuni. 2004. Female Genital Cutting 

in the Demographic and Health Surveys: A Critical and Comparative Analysis.

8. Stallings, Rebecca. 2004. Child Morbidity and Treatment Patterns.

9. Rutstein, Shea O., and Iqbal H. Shah. 2004. Infecundity, Infertility, and Childlessness in 

Developing Countries.

10. Mukuria, Altrena, Jeanne Cushing, and Jasbir Sangha. 2005. Nutritional Status of Children: 

Results from the Demographic and Health Surveys, 1994–2001.

11. Mukuria, Altrena, Casey Aboulafia, and Albert Themme. 2005. The Context of Women’s Health: 

Results from the Demographic and Health Surveys, 1994-2001.

12. Yoder, P. Stanley, Noureddine Abderrahim, and Arlinda Zhuzhini. 2005. L’excision dans les 

Enquêtes Démographiques et de Santé: Une Analyse Comparative.

13. Garenne, Michel, and Julien Zwang. 2006. Premarital Fertility and Ethnicity in Africa. 

14. Westoff, Charles F. 2006. New Estimates of Unmet Need and the Demand for Family Planning.

15. Fort, Alfredo L., Monica T. Kothari, and Noureddine Abderrahim. 2006. Postpartum Care: Levels 

and Determinants in Developing Countries.

16. Khan, Shane, Vinod Mishra, Fred Arnold, and Noureddine Abderrahim. 2007. Contraceptive 

Trends in Developing Countries. 

17. Johnson, Kiersten, and Yuan Gu. 2009. Men’s Reproductive Health: Findings from the 

Demographic and Health Surveys, 1995-2005. 

18. Garenne, M. Michel. 2008. Fertility Changes in Sub-Saharan Africa.

19. Khan, Shane, and Vinod Mishra. 2008. Youth Reproductive and Sexual Health.

20. Kishor, Sunita, and Lekha Subaiya. 2008. Understanding Women’s Empowerment: A 

Comparative Analysis of Demographic and Health Surveys (DHS) Data.

21. Mishra, Vinod, Shane Khan, Li Liu, and Benny Kottiri. 2008. Medical Injection Use and HIV in 

Sub-Saharan Africa.

22. Mishra, Vinod, Amy Medley, Rathavuth Hong, Yuan Gu, and Bryant Robey. 2009. Levels and 

Spread of HIV Seroprevalence and Associated Factors: Evidence from National Household 

Surveys. 

23. Sneeringer, Stacy E. 2009. Fertility Transition in Sub-Saharan Africa: A Comparative Analysis of 

Cohort Trends in 30 Countries.