Series 23

No. 17

Birth Expectations

of Women in the

United States, 1973–88

February 1995
Copyright information

All material appearing in this report is in the public domain and may be

reproduced or copied without permission; citation as to source, however, is

appreciated.

Suggested citation

Peterson, LS. Birth expectations of women in the United States: 1973–88.

National Center for Health Statistics. Vital Health Stat 23(17). 1995.

Library of Congress-in-Publication Data

Peterson, Linda S.

Birth expectations of U.S. women: 1973 to 1988 / [by Linda S. Peterson].

p. cm. — (Vital and health statistics. Series 23, Data from the national

survey of family growth; no. 17) (DHHS publication; no. (PHS) 95-1993)

‘‘February 1995.’’

Includes bibliographical references.

ISBN 0-8406-0501-3

1. Fertility, Human—United States—statistics. 2. Population

forecasting—United States—statistics. I. National Center for Health Statistics

(U.S.) II. National Survey of Family Growth (U.S.) III. Title. IV. Series. V. Series:

DHHS publication; no. (PHS) 95-1993.

[DNLM: 1. Birth Rate—United States—statistics. 2. Pregnancy— United

States—statistics. 3. Family Planning—United States— statistics. 4. Population

Growth—United States—statistics. W2

A N148vw no. 17 1995]

HB901.P48 1995

304.6’32’097309047—dc20

DNLM/DLC 94-33453

for Library of Congress CIP
Birth Expectations

of Women in the

United States, 1973–88

Series 23:

Data From the National Survey of Family

Growth

No. 17

Statistics collected in 1973, 1982, and 1988 on children ever born and future

births expected are presented. The statistics are shown for women 15–44 years

of age at each survey date, by age, race, and parity. The data are also shown

for birth cohorts of U.S. women, as surveyed in 1973, 1982, and 1988.

Hyattsville, Maryland

February 1995

DHHS Publication No. (PHS) 95-1993

Vital and

Health Statistics

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Public Health Service

Centers for Disease Control and Prevention

National Center for Health Statistics
National Center for Health Statistics

Jack R. Anderson, Acting Director

Jennifer H. Madans, Ph.D., Acting Deputy Director

Jacob J. Feldman, Ph.D., Associate Director for Analysis,

Epidemiology, and Health Promotion

Gail F. Fisher, Ph.D., Associate Director for Planning and

Extramural Programs

Peter L. Hurley, Associate Director for Vital and Health

Statistics Systems

Robert A. Israel, Associate Director for International

Statistics

Stephen E. Nieberding, Associate Director for

Management

Charles J. Rothwell, Associate Director for Data

Processing and Services

Monroe G. Sirken, Ph.D., Associate Director for Research

and Methodology

Division of Vital Statistics

Mary Anne Freedman, Acting Director

James A. Weed, Ph.D., Deputy Director

William D. Mosher, Ph.D., Chief, Family Growth and Survey

Branch

Joseph D. Farrell, Chief, Systems and Programming Branch

Cooperating Agencies

The National Survey of Family Growth is jointly planned

and funded by the National Center for Health Statistics, the

National Institute of Child Health and Human Development,

and the Office of Population Affairs, all of the U.S.

Department of Health and Human Services.
Contents

Introduction............................................................................................ 1

Summary of principal findings............................................................................. 2

Source and limitations of the data .......................................................................... 5

The National Survey of Family Growth ................................................................... 5

Concept of birth expectations ........................................................................... 5

Women’s uncertainty about their birth expectations ......................................................... 5

Findings............................................................................................... 6

Trends, by birth cohort ................................................................................ 6

Race ............................................................................................... 6

Children ever born at ages 39–44 ........................................................................ 7

Parity .............................................................................................. 8

Birth expectations, cohort fertility, and the total fertility rate .................................................. 8

Data comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Comparison of the National Survey of Family Growth and Current Population Survey Estimates . . . . . . . . . . . . . . . . . . . . 11

Single number of expected births versus the midpoint of a range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Minimum and maximum average additional births expected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

List of detailed tables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Appendixes

I. Technical notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

II. Definition of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

III. Items on the 1988 National Survey of Family Growth questionnaire related to birth expectations. . . . . . . . . . . . . . . . . . 35

Text figures

1. Average total births expected per white woman, by year of birth: United States, 1982 and 1988................... 3

2. Average total births expected per black woman, by year of birth: United States, 1982 and 1988................... 3

3. Average total births expected, per ever-married white woman first married by 1973, by year of birth: United States,

1973, 1982, and 1988 ............................................................................... 4

4. Average cohort fertility and average total births expected per woman by year of birth: United States............... 9

Text tables

A. Average total births expected in 1973 and average children ever born in 1982 and 1988 per ever-married woman,

by year of birth: United States ....................................................................... 7

B. Average total births expected in 1973 and average children ever born in 1982 and 1988 per ever-married woman

first married before the 1973 survey, by year of birth: United States ......................................... 7

C. Average total births expected per woman based on the National Survey of Family Growth and per ‘‘reporting’’

woman based on the Current Population Survey for women 18–34 years of age: United States, 1988 . . . . . . . . . . . . . . 12

iii
Birth Expectations

of Women in the

United States: 1973–88

by Linda S. Peterson, M.A., Division of Vital Statistics

Introduction

Since its inception in 1973, the National Survey of Family

Growth (NSFG) has included questions on the number of

births women expect to have in the future. The number of

children already born to a woman plus the additional births

she expects provide an estimate of the total number of births

she expects to have in her lifetime. For a given population,

birth expectations provide an estimate of future family size

and perhaps a leading indicator of future trends in the birth

rate. This report analyzes trends in the birth expectations of

women in the United States based on data from three cycles of

the NSFG—Cycle I (1973), Cycle III (1982), and Cycle IV

(1988). Trends by age, race, parity, and marital status are

presented, and the consistency of birth expectations for the

same birth cohorts of women as surveyed in 1973, 1982, and

1988 is analyzed.

National data on women’s birth expectations have been

collected in the United States since the 1950’s. It became clear

at that time that traditional population projections, based

mainly on current and past birth rates, did not accurately

predict the ‘‘baby boom’’ that occurred in the late 1940’s and

1950’s. It was hoped that women’s own predictions of their

future fertility could be used to improve assumptions about

future birth rates, and thus the accuracy of population

projections (1).

Assumptions about the future fertility of U.S. women are

critical to the projected size of the U.S. population. Small

differences in assumed future birth rates or completed cohort

fertility imply large differences in population. The latest

population projections done by the Bureau of the Census

illustrate their importance. As recently as 1985, the total

fertility rate (TFR) in the United States was 1.84, but by 1990,

it was 2.08 births per woman (table 1). Assuming that the TFR

reaches 2.12 births per woman in the year 2050, the population in that year is projected at 383 million (2). Assuming

instead a trend in the TFR that reaches 1.83 births per woman

in the year 2050, while holding the mortality and migration

assumptions constant, the population is projected at 340

million in the year 2050. Thus, a difference of only 0.3 child

per woman in the assumed TFR in 60 years produces a

difference of 43 million people (2).

Birth expectations were first asked of a national sample of

women in 1955, and in 1960 in the Growth of American

Families (GAF) studies. Subsequently, birth expectations have

been collected in a variety of national surveys, including the

National Fertility Studies in 1965 and 1970, the National

Survey of Family Growth in 1973, 1976, 1982, and 1988, and

the Census Bureau’s Current Population Surveys (CPS) for

most years since 1971.

Ways of using birth expectations data for predicting future

birth rates has long been debated. Women do not perfectly

predict their future births. According to a variety of studies,

women tend to underproject or overproject their future fertility

to varying degrees at the individual and aggregate levels

(1,3–8). At the same time, the level and trend in birth

expectations has acted as a leading indicator of a recent

increase in the TFR. The relationship between birth expectations on the one hand, and past, current, and future birth rates

on the other, continues to evolve as U.S. birth rates change.

This report is intended to improve our understanding of the

conditions under which birth expectations provide useful

information for predicting future birth rates.

The author would like to thank Dr. William F. Pratt of the National Center for

Health Statistics, Mr. Arthur A. Campbell of the National Institute of Child

Health and Human Development, and Dr. Martin O’Connell of the U.S.

Bureau of the Census, for their helpful consultation during the preparation of

this report.

1
Summary of

principal findings

In 1988 women ages 15–44 in the United States expected

an average of 2.22 total births in their lifetime, 1.22 of which

were children already born and 1.00 of which was expected in

the future (table 2). In 1982 women ages 15–44 had expected

2.38 total births per woman, so the average declined by

7 percent (0.16 child per woman) from 1982 to 1988. Although

in 1982 the birth expectations of older women exceeded those

of younger women (for example, 2.81 for women ages 40–44

compared with 2.22 for women ages 25–29), by 1988 there

were no significant differences in birth expectations between

any of the 5-year age groups; the averages ranged from 2.13 to

2.34 per woman (table 2).

Among ever-married women ages 15–44 at each survey

date, average birth expectations were higher as might be expected.

They declined from 2.80 children on average in 1973, to 2.47 in

1982 and 2.32 in 1988. The expectations of black ever-married

women ages 40–44 dropped by almost two children per woman

during the 1973–88 period (from 4.26 to 2.53) (table 3).

Birth expectations are usually interpreted in relation to

other available fertility measures, such as completed cohort

fertility or the TFR. Completed cohort fertility refers to the

average number of children ever born to a birth cohort of

women at the end of their childbearing years. Information on

completed fertility for most women currently of reproductive

age will not be available for some years, that is, until each

cohort ages out of the childbearing years. On the other hand,

the TFR is a measure of current fertility in a given year or

other period. It is based on the age-specific birth rates for a

population of women in that period.

According to the 1982 NSFG, women born during 1947–49

and in the 33–35-year-old age group in 1982 expected 2.22

births per woman over their lifetime (table 4). Based on U.S.

birth registration data, it is estimated that women 40–42 years

of age on January 1, 1989, will have had 2.07, 2.12, and 2.17

births per woman, respectively, upon completing their childbearing. This was between 2 and 7 percent less than the

average expected by the combined cohorts about 6 years

earlier (tables 1 and 4). (These estimates of completed cohort

fertility have been adjusted for additional projected fertility as

the women pass through their 40’s, as described in footnote 2

of table 1). It is not surprising that expected fertility exceeded

the estimated completed fertility for the full cohorts of women,

given that the unmarried and childless women in the cohorts

are likely to expect more births on average than they will

eventually have (6). None of these differences, however, is

statistically significant.

Also in recent years, birth expectations have exceeded the

annual TFR. In 1982, when women ages 25–29 were expecting 2.22 total births on average, the TFR was only 1.83; in

1988, when women ages 25–29 were expecting 2.33 births per

woman, the TFR was 1.93 (tables 1 and 2). Thus, in 1982 and

in 1988 women of reproductive age were bearing children at

rates that were 17 or 18 percent lower than the levels implied

by the birth expectations of women ages 25–29 in those years.

This divergence suggested that the TFR should rise in the

future. The high level of expectations relative to the TFR and

age-specific birth rates has for some time suggested that many

women who delay childbearing plan to compensate for this

delay later in life. In fact, the TFR for the United States did

increase to over two children per woman in 1989 and 1990

(table 1), due in part to increases in the birth rates for women

in their 30’s and 40’s (9).

All but one of the 3-year birth cohorts of white women

born during the period 1944–67 reduced their birth expectations between 1982 and 1988. The reductions were small

(9 percent or less), and none were statistically significant

(table 3 and figure 1). This downward direction of change is

consistent with findings from previous studies and may be

explained by the occurrence of unforeseeable events, such as

separation, divorce, infertility, or remaining single, events

which would tend to depress aggregate birth expectations

within cohorts of women of all marital and parity statuses over

time (6).

Among birth cohorts of black women, there was less

consistency in the direction of change in expectations from

1982 to 1988 than for white women, probably due in part to

greater sampling variability (see appendix I, Technical notes).

Birth cohorts of black women who were over age 20 in 1982

had reduced their expectations by as much as 15 percent in

1988 (table 4 and figure 2). Black teen cohorts of 1982

experienced an opposite trend, however, increasing their expectations by as much as 16 percent (2.11 to 2.45 for the 1962–64

cohort) (table 4 and figure 2). Young black cohorts started out

in 1982 with low expectations relative to young white cohorts

(1.95 versus 2.36 for women ages 15–17 in 1982), but then

experienced an upward trend in expected births as a consequence of apparently unexpected childbearing (table 4 and

figure 2). The cohort changes for black women, however, were

not statistically significant.

An analysis of birth cohorts for the longer time period,

1973–88, must be restricted to ever-married women since

never-married women were not interviewed in 1973. Ever2
married white women born 1944–55 revised their average

expectations downward between 1973 and 1988 by an insignficant 4–7 percent (table 5). Ever-married white women born

1944–55 who had their first marriage before the 1973 survey

maintained virtually the same average total births expected

over a 15-year period from 1973 to 1988, in the range of 2.3 or

2.4 expected births (table 6 and figure 3). Likewise, a comparison of total expected births in 1973 and children ever born in

1988—for birth cohorts of white women who reached ages

39–41 in 1988—showed virtually no difference, controlling

for the timing of first marriage. For example, white, evermarried women born 1947–49 and first married before the

1973 survey expected 2.29 total births on average in 1973 and

had had an average of 2.32 children ever born by 1988

(table 6). Ever-married white women in 1973 were excellent

predictors of their cohort fertility 15 years later, and they

tended to achieve the births they expected. It is not possible to

reliably analyze data for ever-married black women for the

15-year period, due to the small number of black women in

the 1988 sample who were first married before the date of the

1973 survey.

Both in 1982 and 1988, the two-child family was by far

the most popular expected family size for women ages 15–44.

In 1988, 44 percent of women expected to have two children

1965 67 1962 64 1959 61 1956 58 1953 55 1950 52 1947 49 1944 46

Year of birth

0

0.5

1.0

1.5

2.0

2.5

3.0

Total births expected

1982 1988

Figure 1. Average total births expected per white woman, by year of birth: United States, 1982 and 1988

1965 67 1962 64 1959 61 1956 58 1953 55 1950 52 1947 49 1944 46

Year of birth

0

0.5

1.0

1.5

2.0

2.5

3.0

Total births expected

1982 1988

Figure 2. Average total births expected per black woman, by year of birth: United States, 1982 and 1988

3
in their lifetime, and in 1982, 43 percent did (table 7). At the

same time, the proportion of women expecting to remain

childless increased during the period, from 7 to 9 percent, and

the proportion expecting just one child increased from 12 to

14 percent, both statistically significant increases (table 7).

Unmarried women, who are relatively less certain of their

birth expectations (table 8), were primarily responsible for

these increases (tables 9 and 10).

1953 55 1950 52 1947 49 1944 46

Year of birth

0

0.5

1.0

1.5

2.0

2.5

3.0

Total births expected

1973 1982 1988

Figure 3. Average total births expected, per ever-married white woman first married by 1973, by year of birth: United States, 1973, 1982,

and 1988

4
Source and limitations of

the data

The National Survey of Family Growth

The findings in this report are based on data from the

NSFG, conducted by the National Center for Health Statistics

(NCHS), in which national samples of women 15–44 years of

age were interviewed in 1973, 1982, and 1988. In this report,

data are shown for Cycle I, Cycle III, and Cycle IV. In Cycle

I the sample included ever-married women ages 15–44; the

only never-married women included in 1973 were the small

population who had their own children living with them. In

Cycles III and IV the sample included all women ages 15–44,

regardless of marital status, in the civilian noninstitutionalized

population of the United States. Alaska and Hawaii were

excluded from Cycle III but included in Cycle IV. Cycle I was

based on 9,797 interviews, Cycle III on 7,969, and Cycle IV

on 8,450 interviews. The interview includes information on a

number of topics related to childbearing, including past and

expected future births, fecundity and infertility, contraceptive

use, and use of health care related to childbearing.

Concept of birth expectations

Since its inception in 1973, the NSFG has included

questions on the birth expectations of women. The questions

are as follows (also see appendix III):

1. Looking to the future, do you (and your husband/cohabiting

partner) intend to have a(nother) baby at some time?

2. (Not counting the bab(y/ies) you have already had), how

many (more) do you (and your husband/cohabiting partner) intend to have?

3. Of course, sometimes things do not work out exactly as we

intend them to, or something makes us change our minds. In

your case, how sure are you (and your husband/cohabiting

partner) that you will have (number/range) (more) bab(y/ies)?

Would you say you are very sure or not very sure?

Those women who answered question 1 that they did not

know whether they intended to have a(nother) baby, or

answered question 2 that they did not know how many they

intended to have, were asked these additional questions:

4. Many people aren’t sure, but still have some idea about

the future. As you expect things to work out for you, what

is the largest number of (additional) babies you (and your

husband/cohabiting partner) expect to have?

5. What is the smallest number of (additional) babies you

(and your husband/cohabiting partner) expect to have?

The use of the term ‘‘intend’’ in questions 1 and 2, and of

‘‘expect’’ in questions 4 and 5 were considered to be tapping a

single dimension in this series of questions, which is referred

to as birth ‘‘expectations’’ throughout this report.

The number of children already born to a woman, plus the

additional births she expects, if any, provide an estimate of

total births she expects to have in her lifetime. If a range of

expected additional births is given instead of a single number,

the average of the range is used as the estimated number of

additional births expected in this report unless otherwise

specified. In Cycle IV of the NSFG, responses for the variable

‘‘additional births expected’’ were obtained for 8,281 of the

8,450 respondents; for the remaining 2 percent of the sample,

data were imputed.

Women’s uncertainty about their

birth expectations

The concept of uncertainty is important to keep in mind in

interpreting aggregate birth expectations. A woman’s expected

family size is likely to change over her lifetime. Studies suggest

that many women make decisions about fertility one birth at a

time, and factors such as work, education, and changes in marital

status have important effects on expected births (5,8).

Although almost all women in the NSFG do provide

either a number or a range of expected births in response to

the series of questions above, a large proportion are not very

certain of their birth expectations. In Cycle IV, 6 percent of

women ages 15–44 could not answer question 1 or 2, but

when followed up with questions 4 and 5, provided a range of

additional births expected (table 8). These women were clearly

uncertain about their responses. Another 25 percent of women

provided a number or a range in response to questions 1 and 2,

but indicated in question 3 that they were ‘‘not very sure’’

about the number or range of expected births they had

provided (table 8). Thus, overall, 31.5 percent of women were

clearly uncertain about their future birth expectations (table 8).

Unmarried women were almost twice as likely to be

uncertain about their birth expectations as married women. In

1988, 42 percent of unmarried women either indicated initially

that they did not know their birth expectations (7 percent), or

indicated that they were ‘‘not very sure’’ about the number

they gave in response to the previous question about future

births expected (35 percent, table 7). Among married women,

22 percent did not know their additional expected births

(6 percent) or indicated that they were ‘‘not very sure’’ about

the number they had given (16 percent) (table 8).

5
Findings

Trends, by birth cohort

Understanding patterns of change in birth expectations

within cohorts of women is essential for applying birth

expectations data to the projection of fertility. How consistent

or stable are the aggregate birth expectations of birth cohorts

of women followed over time? For six of the eight 3-year birth

cohorts of women for which data are available in 1982 and

1988, average expected births declined during the period by as

much as 10 percent, but most declines were by less than

5 percent (table 4). For example, women born 1953–55 expected

2.22 total births on average in 1982 and expected 2.12

(5 percent less) in 1988. None of the declines was statistically

significant. In the two cohorts that showed increased expectations, the magnitude was less than 1.5 percent and not statistically significant (table 4).

The birth expectations of birth cohorts of women who

were ever-married at the time of each survey have also shown

high consistency in recent decades. For each of the five 3-year

birth cohorts for which there are data in both 1973 and 1988

(those born 1944–58 and 15–29 years of age in 1973), average

expectations were revised downward over the period, by 0.4 to

7 percent (table 5). None of the declines was statistically

significant. For example, ever-married women born 1950–52

expected 2.31 total births on average in 1973 (when they were

21–23 years of age), and in 1988 ever-married women born

those same years expected 2.24 total births (when they were

36–38 years of age), representing a decline of 3 percent

(table 5). This reduction is not surprising, given that members

of the cohorts who married for the first time later than 1973

are represented in 1988 but not in 1973, and older age at first

marriage is associated with relatively lower birth expectations

and fertility (6).

When the timing of first marriage is controlled for,

aggregate expectations for birth cohorts in 1973 and 1988

show an even closer correspondence. When the 1982 and

1988 study populations are restricted to women who were

ever-married at the time of the 1973 survey, there are no

statistically significant changes within cohorts from 1973 to

1982 or from 1973 to 1988. In contrast to the downward

direction of change found for full ever-married cohorts in

each year (table 5), there is a pattern of slight upward

change (table 6). For example, cohorts of white women

born 1950–52 and 1947–49, who were 21–26 years of age

in 1973, expected 2.31 and 2.29 average births in 1973,

respectively, and 3 percent more in 1988 (table 6 and

figure 3). This change was not statistically significant,

however.

Overall, aggregate birth expectations of birth cohorts of

women in the NSFG surveys are remarkably stable over time,

especially after controlling for the timing of first marriage.

When the timing of first marriage was controlled for, the

pattern of declining cohort expectations over time disappears

and women in the aggregate predict their birth expectations 15

years into the future accurately.

Race

As just shown, birth expectations are remarkably stable

for all races combined. But this stability is less apparent within

race groups, especially at very young ages. In 1982, young

black women just entering their childbearing years tended to

have lower expectations than white women of similar age, but

they also tended to revise their expectations upward over time

rather than downward. For example, black women born 1965–67

and 1962–64, the youngest cohorts for which we have data in

1982, expected an average of 1.95 and 2.11 births, respectively (table 4 and figure 2). In 1988, these cohorts had revised

their expectations upward to 2.11 and 2.45 births, an 8- and

16-percent increase, respectively. On the other hand, white

women of the same cohorts expected 2.36 and 2.51 births in

1982, respectively, but then reduced their expectations slightly

as of 1988 by 2 and 5 percent, respectively (table 4 and

figure 1). These changes, however, were not statistically significant for either black or white women.

These different patterns for young white and black women

may be a result of differences in the timing of childbearing.

Black teenage women had a higher average number of children already born than white teenage women. In 1988 black

women 15–19 years of age had had 0.21 births per woman on

average compared with 0.06 average births for white women

of those ages (table 2). A large proportion of births to women

15–19 years of age are unintended, 73 percent for births

occurring from 1984 to 1988 (10). Young black women who

have experienced unintended births may tend to state that they

expect no future births, and thereby reduce the average total

births expected by young black women. Birth expectations

data for young black women may reflect their wish to avoid

further unintended childbearing, while the birth expectations

for most young white women do not reflect such experience.

This hypothesis has not been tested here, however.

6
Although fertility trends for Hispanic women were recently

projected separately from those for non-Hispanic white women

and non-Hispanic black women (2), the birth expectations of

Hispanic women are not analyzed separately in this report.

Given the limited number of Hispanic respondents in the

NSFG, it would be impossible to reliably analyze trends by

birth cohort for this group at the national level. However,

larger samples of Hispanic women are planned for future

cycles of the NSFG.

Children ever born at ages 39–44

How well do the aggregate birth expectations of a cohort

predict its eventual completed cohort fertility? Theoretically,

as women achieve greater control over fertility through the

expanded use of contraception, the correspondence between

women’s expectations and their future children born should

improve, both for individuals and in the aggregate. NSFG

1973 estimates of the average number of total births expected

by female birth cohorts who were ever-married in 1973, and

the eventual average number of children born to the birth

cohorts toward the end of their childbearing years (39–44-yearolds), are compared in tables A and B.

Table A shows the estimates for the female populations

that were ever-married at the time of each survey. The birth

cohorts are not consistent in terms of the timing of first

marriage. For example, cohorts of ever-married women in

1982 and 1988 would include many women who first married

later than 1973 and whose fertility would tend to be lower than

that of the early marriers of the same birth cohorts. Based on

the populations of ever-married women at the time of each

survey, the correspondence between the average number of

total births expected and the eventual number of children born

to the cohorts 39–44 years of age is within a 5-percent margin

for the period 1973–82 and within a 9-percent margin for the

15-year period 1973–88. For example, in 1973, ever-married

women born 1941–43 expected an average of 2.76 total births;

in 1982, ever-married women born those same years and near

the end of their childbearing years at 39–41 years of age, had

borne 2.63 children per woman on average, or 5 percent less

than expected. Women who were born 1947–49 and evermarried in 1973, expected 2.33 total births on average; and

women born those same years and ever-married in 1988, had

had 2.21 births per woman, 0.12 births per woman (5 percent)

less than the expectations. Neither of these differences were

statistically significant. Since fertility is not totally complete

by 39–41 years of age or 42–44 years of age, the actual

correspondence between predicted and completed fertility

would be even closer. For all of the cohorts analyzed, more

births were expected in 1973 than were eventually born to the

cohorts by the later survey date. Again, this differential is not

surprising, given the compositional differences of the cohorts in

earlier and later years in terms of the timing of first marriage.

Table B shows the relation between expected births in

1973 and cumulative fertility at 39–41 years of age and at

42–44 years of age for birth cohorts of women who were first

married in or before September 1973, the midpoint of interviewing for the 1973 survey. After thus controlling for the

timing of first marriage, the 1973 cohort predictions were

closer to the cumulative aggregate births at 39–41 years of age

and at 42–44 years of age in 1982 and 1988. None of the

differences was statistically significant. For example, evermarried women born 1947–49 expected 2.33 births on average

in 1973 (24–26-year-olds), and in 1988 (39–41-year-olds) this

group had had 2.36 births.

In the past, most of the analyses of the consistency of

aggregate birth expectations and eventual completed fertility

have been done for married women (1,3–8); few analyses have

been done on women of all marital statuses combined. The

Table A. Average total births expected in 1973 and average children ever born in 1982 and 1988 per ever-married woman, by year of

birth: United States

Year of birth

1973 1982 1988

Age

Average

total births

expected Age

Average

children

ever born Age

Average

children

ever born

1947–49 .................. 24–26 2.334 33–35 2.010 39–41 2.209

1944–46 .................. 27–29 2.471 36–38 2.382 42–44 2.266

1941–43 .................. 30–32 2.763 39–41 2.631 45–47 . . .

1938–40 .................. 33–35 2.980 42–44 2.968 48–50 . . .

Table B. Average total births expected in 1973 and average children ever born in 1982 and 1988 per ever-married woman first married

before the 1973 survey, by year of birth: United States

Year of birh

1973 1982 1988

Age

Average

total births

expected Age

Average

children

ever born Age

Average

children

ever born

1947–49 .................. 24–26 2.334 33–35 2.238 39–41 2.364

1944–46 .................. 27–29 2.471 36–38 2.489 42–44 2.331

1941–43 .................. 30–32 2.763 39–41 2.753 45–47 . . .

1938–40 .................. 33–35 2.980 42–44 3.015 48–50 . . .

7
NSFG data for 1982 and 1988 represent full cohorts of U.S.

women. Average total births expected by women of all marital

statuses who were 33–38 years of age in 1982 and the number

of children born to these cohorts as of 1988 (39–44-year-olds)

are quite consistent. For example, women born 1947–49

expected in 1982, 7 percent more births than they eventually

had by 1988 at 39–41 years of age (2.22 versus 2.07) (table 4).

Black women born 1947–49 expected in 1982, 11 percent

more total births than they eventually had at 39–41 years of

age in 1988, a larger differential than the 5-percent excess

births predicted by white women born those years (table 4).

This pattern whereby expectations at an earlier date tend

to exceed achieved fertility at a later date, within full cohorts,

is partially explained by the parity, marital, and other characteristics of the cohorts. Among young women, the larger the

proportion of a cohort that is unmarried or childless, the

greater is the likelihood that expectations will exceed future

completed fertility. Both unmarried and married women who

are childless, have in the past been found to eventually achieve

only about 80 percent of the births they expected when they

were 18–24 years of age (6).

The NSFG data show, however, that when the timing of

first marriage is controlled for, cohorts of ever-married women

have almost perfectly predicted their future fertility as much as

15 years into the future.

Parity

How did women’s orientations toward family size change

in the 1980’s? Is the traditional preference for two children

being eroded by growing numbers of women or couples who

expect just one child or none at all? The answer to the latter

question is a qualified no.

The proportion of women with expectations for a twochild family did not decline during the 1980’s. In 1988 as in

1982, almost one-half of all women 15–44 years of age

intended to have two children in their lifetime: 43 percent in

1982 and 44 percent in 1988 (table 7). During the same period,

the proportion of women expecting to remain childless

increased, from 7 percent in 1982 to 9 percent in 1988, and the

proportion expecting just one child increased from 12 to

14 percent. Both of these increases were statistically significant. They were offset mainly by a statistically significant

decline in the proportion of women expecting four or more

children, from 14 percent in 1982 to 11 percent in 1988.

Although the propensity to expect a future birth declined

slightly among women of each of the parity levels (0, 1, 2, and

3), from 1982 to 1988, only the decline for single-parity

women was statistically significant. In 1982, 61 percent of

single-parity women expected to have a future birth but in

1988 only 53 percent of single-parity women did. Thus,

almost one-half of single-parity women in 1988 (47 percent)

expected no more births.

While both black and white women changed their fertility

orientations in the direction of smaller families, the percentage

changes were larger for black women. In 1982, 36 percent of

black women with one child expected no more births, but in

1988 the proportion had risen to 49 percent; and among black

women with two children, the proportion expecting no more

births rose from 67 percent in 1982 to 78 percent in 1988

(table 7).

The shift in favor of smaller family size, however, was not

shared equally among all marital status groups. Unmarried

women (one-half of women 15–44 years in age in 1988 and

48 percent in 1982) were responsible for most of the increased

expectations for both childlessness and having only one child

(tables 9 and 10). Since the level of uncertainty about birth

expectations is relatively high among unmarried women

(table 8), the shift in favor of smaller family size must be

interpreted cautiously. In general, however, the data do suggest

that the prevalence of the two-child family may decline in the

coming decades as more women choose to remain childless or

to have just one child.

Birth expectations, cohort fertility, and

the total fertility rate

Comparisons of birth expectations data with other available fertility measures, such as completed cohort fertility or

TFR’s, can help demographers use birth expectations to

project fertility. The TFR is a measure of current fertility and

refers to a given period, often a year. It is derived by summing

the age-specific birth rates for a population of women of

reproductive age in the given period. Completed cohort fertility refers to the average total number of children ever born to

a birth cohort of women when their childbearing is complete,

for example, by age 47. The TFR, although it reflects birth

rates in a given year or period, can also be interpreted as a

hypothetical measure of completed fertility for a synthetic

cohort of women assumed to pass through life bearing children at the age-specific rates in the given year. The trend for

the United States from 1957 through 1990 appears in table 1

(9,11,12).

In 1988 women 25–29 years of age expected an average

of 2.33 lifetime births (table 2). Estimated completed fertility

for women ages 40, 41, and 42 on January 1, 1989, is 2.07,

2.12, and 2.17, respectively (13–17) (see note 2 of table 1 for

derivation of estimates of completed cohort fertility). The

expectations of young women 25–29 years of age in 1988

exceed the estimated completed fertility of women in their

earliest 40’s at the time by about 9 percent (the difference

between 2.33 and the average of 2.07, 2.12, and 2.17, above).

Taken literally, birth expectations data imply that the eventual

completed cohort fertility for women born 1959–63 (25–29

years of age in 1988) will exceed the estimated levels of 2.07

to 2.17 of women born 1947–49 (table 1). Such a trend would

represent a reversal of a long-term downward trend in cohort

fertility. Cohort fertility historically has declined steadily, for

example, from 3.11 births per woman for the cohort born in

1936 to 2.07 births per woman for the cohort born in 1949

(table 1).

A more probable scenario is that the cohort of women

25–29 years of age in 1988 will reduce their birth expectations

over time, as cohorts of women of all marital statuses combined tend to do (table 4). Thus, they may ultimately bear

8
about 9 or 10 percent fewer children than they expected when

they were 25–29 years of age.

As depicted in figure 4, birth expectations provide hypothetical estimates of completed cohort fertility for birth cohorts

that have not yet completed their childbearing. Average expected

births for each of the 3-year birth cohorts from the 1982 and

1988 NSFG, charted next to available estimates of completed

cohort fertility from the birth registration system, suggest that

cohort fertility will remain around two children per woman for

the next couple of decades (figure 4).

The recent birth expectations of women 25–29 years of

age also have exceeded the hypothetical family size implied

by the TFR. In 1988, when women 25–29 years of age

expected an average of 2.33 births per woman, the TFR was

only 1.93; and in 1982, the expectations of women 25–29

years of age averaged 2.22, while the TFR was only 1.83

(tables 1 and 2).

The historical differentials in levels of birth expectations

and the TFR can provide insights for interpreting recent birth

expectations data. There traditionally has been a difference

between women’s average total births expected and the TFR.

In the late 1950’s, when the TFR in the United States reached

3.7 births per woman, the expectations data that was available

for young married women at the time indicated a lower level

of anticipated future fertility, around 3.2 children per woman.

Upon completing their childbearing, in fact, these young

women of the 1950’s did have approximately 3.2 children on

average (4). Subsequently, in the 1970’s, when the TFR fell to

an extreme low (for example, 1.74 in 1976; table 2), birth

expectations had declined also, but to a lesser degree, and they

declined more slowly than the TFR (4). During the period of

the late 1970’s through the early 1980’s, available birth

expectations estimates from the CPS averaged higher than the

national TFR (9,18). Based on this historical relationship

between the two measures, Moore suggested in retrospect that

birth expectations informed us that the total fertility rate was

artificially high in the late 1950’s and early 1960’s and could

not be sustained at that level. He also suggested that birth

expectations data available in the 1970’s (for example, estimates from the Current Population Survey of between 2.16

and 2.07 for 1976–79 for women 18–34 years of age (18)

implied that the extremely low TFR that persisted through the

1970’s (for example, ranging from 1.74 to 1.81 for 1976–79)

(table 2) was temporary. He anticipated that the TFR would

rise in the future to correspond more closely to average

expected births (4). In the late 1980’s, a rise in the TFR

became perceptible (table 2).

The unusually low TFR that persisted through most of the

1970’s and 1980’s was a function of changes that were occurring

in the age pattern of fertility. Most importantly, women who

reached their late teens and 20’s in the 1970’s and 1980’s were

tending to delay both marriage and childbearing until later in their

reproductive lives, relative to what women had done in the past.

This tendency lowered the birth rates for women in their late

teens and 20’s beginning in the early 1970’s (9). Secondly, many

women in their 30’s in the late 1970’s had already experienced

the traditional age pattern of childbearing whereby most of their

children had been born when they were in their 20’s, so their

birth rates at the time were also low.

Young women’s birth expectations in 1982 and 1988,

which averaged above two births per woman (table 2), suggest

that women who delayed childbearing fully intended to compensate later in their reproductive cycles for this delay.

Clearly, some compensation is occurring, given that the rise in

the TFR in 1988, 1989, and 1990 (table 1) is partially attributable to rising birth rates among women in their 30’s (9). The

issue of to what degree the delayers of the 1970’s and 1980’s

will be able to fulfill their expectations later in life is a

question currently under investigation (19). If the TFR persists

at a level above two children per woman, then the data on

birth expectations will have served their purpose—they will

have predicted such a trend.

The birth expectations of women 25–29 years of age are

chosen for the above comparisons with other fertility measures

Figure 4. Average cohort fertility and average total births expected per woman by year of birth: United States

NOTE: Data for 1982 and 1988 refer to 3-year cohorts centered on given year. TBE is total births expected. NSFG is the National Survey of Family

Growth.

1930 1933 1936 1939 1942 1945 1948 1951 1954 1957 1960 1963 1966 1969 1972

Year of birth

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Births

Cohort fertility TBE,NSFG, 1982 TBE, NSFG,1988

9
for several reasons. First, a large proportion of births to this

group will occur in the future, so the estimates refer mostly to

future fertility and therefore warrant evaluation. At the same

time, many women in this age group will have married,

thereby removing some uncertainty about birth expectations

associated with the never-married status (see table 8). In

addition, the birth rate for women 25–29 years of age is higher

than the birth rates for other 5-year age groups, and therefore

has the largest impact on the level of the TFR. Women 25–29

years of age also contribute the largest portion of annual

births: 31 percent of births in 1990 were to women 25–29

years of age (9).

10
Data comparisons

Comparison of the National Survey of

Family Growth and Current Population

Survey Estimates

Estimates of average birth expectations for U.S. women

vary by data source, as a consequence of different data

collection procedures and estimation methods. For example,

birth expectations are asked differently in the NSFG and in the

CPS. The 1988 NSFG questions are listed previously in the

section, Concept of birth expectations. In the 1988 CPS,

women were asked their birth expectations as follows (20):

1. Looking ahead, do you expect to have any (more) children?

Answer: yes, no, uncertain.

If the answer to the above question was ‘‘yes,’’ the following

question was asked:

2. How many (more) do you expect to have?

There are a number of differences between the CPS and

NSFG data on birth expectations:

1. The CPS questions are briefer than the NSFG questions

and do not ask for a range of future births expected when

a respondent is uncertain.

2. The CPS questions ask how many births the woman

‘‘expects’’ rather than how many she ‘‘intends’’ to have.

3. For married or cohabiting women, the CPS questions ask

about the woman’s expectations alone, not her and her

husband’s or partner’s joint expectations, as in the NSFG.

4. From the CPS, average birth expectations data are estimated using reporting women 18–34 years of age as the

denominator, while in the NSFG, the denominator is all

women 15–44 years of age.

In the CPS, a woman is classified as ‘‘reporting’’ if either

she answered both ‘‘yes’’ to question 1 above and gave a

number in question 2, or if she answered ‘‘no’’ to question 1.

Reporting respondents in the 1988 CPS represented 73 percent

of U.S. women 18–34 years of age (20). Nonreporters in the

CPS (27 percent of U.S. women 18–34 years of age) consisted

of ‘‘uncertain’’ respondents and those whose response was

‘‘incomplete.’’ The ‘‘uncertain’’ component includes those

who indicated that they were uncertain about whether they

expected to have a(nother) baby, or who were uncertain as to

the number they expected to have (combined, about 15 percent

of U.S. women). ‘‘Incomplete’’ cases were those for which the

birth expectations items were incomplete for any reason,

including the respondent’s unavailability for the interview

(about 12 percent of U.S. women) (20). In the CPS, proxy

responses on the woman’s birth expectations were not accepted

from another household member. CPS respondents who were

unavailable for the interview and could not be traced within 1

week of the interview that was conducted with a proxy

respondent from their household were classified as nonreporters on birth expectations in the CPS.

By contrast, the NSFG estimates of average birth expectations refer to total U.S. women. In the NSFG, respondents

who were uncertain about whether they expected any additional births, or about the number they expected, were asked to

give a range—and most of them did. For those who were still

uncertain, or for those who were interviewed but whose

responses were incomplete, imputation was performed. Imputation was necessary for only 169 cases or 2 percent of sample

women. Moreover, although the NSFG Cycle IV overall

survey response rate was approximately 80 percent, the

responses of available sample women on all variables, including birth expectations, were weighted for nonresponse using a

complex weighting procedure designed to reduce the risk of

nonresponse bias; then the responses were adjusted to CPS

population controls (21,22). Thus, in the NSFG, there were no

‘‘nonreporting’’ women due to unavailability for the interview

as there are in the CPS.

As a consequence of methodological differences such as

those described in the preceeding text, NSFG estimates of

women’s average birth expectations differ from CPS estimates. They exceed CPS estimates for reporting women by

11 percent for women 18–24 years of age, 9 percent for those

25–29 years of age, and by a nonsignificant 5 percent for those

30–34 years of age (table C).

For purposes of comparison, the NSFG estimates were

revised in column 2 of table C, using a derived denominator of

NSFG ‘‘reporting’’ women that is as similar as possible to

‘‘reporting’’ women in the CPS. Women who initially said

they were uncertain about whether they intended to have

a(nother) baby were excluded from the denominator. In addition, those who expected to have a(nother) baby but were

uncertain about the number they expected, were excluded.

However, those who expected one or more future births, and

gave a range, were retained, as was done in the CPS; and the

lower bound of the range, instead of the midpoint, was taken

as the number of additional births expected, as was conservatively done in the CPS (table C). In making these adjustments,

11
5.5 percent of U.S. women 18–34 years of age were removed

from the denominator as the equivalent of ‘‘uncertain’’ nonreporters. Also, removing the NSFG imputed cases (2.3 percent

of U.S. women 18–34 years of age) brought the NSFG

proportion of U.S. women 18–34 years of age who can be

categorized as nonreporters—as defined by the CPS—to 7.8 percent. This was still much lower than the 27 percent in the CPS.

Once the NSFG estimates have in this manner been made as

methodologically consistent as possible with the CPS estimates

(table C), the NSFG-CPS differential is narrowed but remains

statistically significant for the age groups 18–24 and 25–29.

This remaining differential between the two sources is

probably a function of the varying size and characteristics of

the group of nonreporting women in each survey, as well as

other factors such as the different wording of the questions,

their relative placement on the questionnaire, and the overall

content of each of the surveys. For example, the NSFG is a

survey about having babies and this context may predispose

women to answering questions about having additional babies

in a more positive manner than does the context provided by

the CPS, in which the bulk of questions relate to labor force

participation.

Also, it is possible that nonreporting women in the CPS

(for example, 27 percent of total women 18–34 years of age in

1988), had they reported on lifetime births expected, would

have high average birth expectations relative to reporting

women in the CPS. If this were true, the inclusion of a large

portion of this nonreporting group in the NSFG would positively affect the NSFG estimates. It is known that the CPS

sample women who were nonreporters on birth expectations

are disproportionately young, single, childless, and of minority

status (20). Thus, proportionately more of these groups are

represented in the NSFG estimates. Further exploration of

both data sources is needed to determine whether these groups

have relatively high birth expectations and whether, therefore,

the greater representation of these groups in the NSFG fully

explains the remaining differential in average birth expectations from the two sources.

Single number of expected births versus

the midpoint of a range

The NSFG has always asked for a range of additional

births expected when a woman indicates that she does not

know her birth expectations. It is possible to tentatively

evaluate the effect of this approach on aggregate birth expectations, based on data from Cycle I (1973). In Cycle I, women

who initially reported a specific number of additional expected

births, but indicated they were ‘‘not very sure’’ about the

number, were asked the largest and smallest number of births

they expected to have in the future. For example, a woman

might have been asked if she intended more births, and said

‘‘yes.’’ She was then asked how many more she intended to

have, and said ‘‘two.’’ She was then asked how sure she was

that she would have two, and said ‘‘not very sure.’’ She was

then asked the largest number of additional births she expected,

and answered ‘‘two.’’ Finally, she was asked the smallest

number of additional births she expected and said, ‘‘one.’’ So

her ‘‘single’’ number was ‘‘two’’ and the average of her range

was (1+2)/2 = 1.5. Of the 9,797 total women in the sample,

1,143 gave both a single number and a range of expected

births.

Two types of weighted estimates of average additional

births expected were calculated for this group—one based on

the single numbers and another based on averages of the

ranges. Based on the single numbers, the group expected 1.72

additional births per woman; based on the means of the

ranges, the same women expected 1.63 additional births per

woman (table 11). Thus, averaging the ranges produced the

lower estimate. The direction of this differential was consistent

across age groups 15–19 through 40–44. The use of the lower

bound of the range would further reduce the ‘‘range’’ estimate.

Thus, among this select subsample, taking an average of the

range rather than the lower bound of the range, produced an

estimate closer in value to that based on the single number of

expected births.

Table C. Average total births expected per woman based on the National Survey of Family Growth and per ‘‘reporting’’ woman based on

the Current Population Survey, for women 18–34 years of age: United States, 1988

Age group

Source and population

National survey of

family growth

Current population

survey

Women ages

18–34

‘‘Reporting’’

women ages

18–341

Reporting

women ages

18–342

18–24 .......................... 2.302 2.228 2.045

25–29 .......................... 2.334 2.294 2.116

30–34 .......................... 2.165 2.109 2.057

1National Survey of Family Growth ‘‘ reporting’’ women include those who initially responded yes or no regarding their intention to have a(nother) baby, and who also initially gave a number (or

range) of additional births they expected to have (if more were expected). ‘‘Initially’’ means in response to the first two direct questions on birth expectations (see appendix III). Thus, these

‘‘reporting’’ women were skipped past the followup questions on ‘‘largest’’ and ‘‘smallest’’ number of births expected. These ‘‘reporters’’ represented 92 percent of U.S. women 18–34 years of age

in 1988. For cases where a range was provided initially, that is, in response to the first two questions on birth expectations, the lower bound of the range was taken as the estimate, as is done in

the Current Population Survey (CPS), in order to make this column of estimates as methodologically consistent as possible with the CPS estimates.

2Reporting women in the CPS are defined as those who were personally available to be interviewed, and who responded yes or no about whether they expected a(nother) birth and also provided

a number or range of additional expected births. In the CPS, in 1988, 73 percent of U.S. women 18–34 years of age were classified as reporting on birth expectations (20). (See tables I, 5, 7, and

C-3 in reference 20 for estimating the standard error of a fertility ratio.)

12
Minimum and maximum average additional

births expected

In Cycle IV of the NSFG, about 9 percent of respondents

provided a range of additional births they expected, for

example, ‘‘1 or 2’’ or ‘‘2 or 3,’’ either spontaneously or in

response to questions 4 and 5 previously mentioned. The

upper and lower bounds of the ranges of expected births may

be used to produce minimum and maximum estimates of

average births expected (23). Minimum and maximum estimates of average expected births for U.S. women, by age and

race, appear in table 12. The differential in minimum and

maximum estimates is largest for white women under age 30.

For example, the estimate of average additional births expected

for white women 20–24 years of age based on the minimum of

the range is 1.80 compared with their maximum estimate of

1.95 future births (table 12). The estimate for white women

20–24 years of age, using the midpoint of any range given, is

1.87 (table 2).

13
References

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14
List of detailed tables

1. Total fertility rate and estimated completed cohort fertility

for women 27 years of age, by year: United States,

specified years, 1957–66 and each year 1969–90 . . . . . . 16

2. Number of women 15–44 years of age and average

number of children ever born, average additional births

expected, and average total births expected, by race and

age: United States, 1982 and 1988 . . . . . . . . . . . . . . . . 17

3. Number of ever-married women 15–44 years of age and

average number of children ever born, average additional

births expected, and average total births expected, by race

and age: United States, 1973, 1982, and 1988 . . . . . . . . 18

4. Number of women born 1938–73 and average children

ever born, average additional births expected, and average

total births expected, by race and year of birth: United

States, 1982 and 1988 . . . . . . . . . . . . . . . . . . . . . . . . . 19

5. Number of ever-married women born 1929–73 and average children ever born, average additional births expected,

and average total births expected, by race and year of

birth: United States, 1973, 1982, and 1988 . . . . . . . . . . 20

6. Number of ever-married women born 1929–73 who were

first married prior to the National Survey of Family

Growth Cycle I (1973) and average children ever born,

average additional births expected, and average total births

expected, by race and year of birth: United States, 1973,

1982, and 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

7. Number of women 15–44 years of age and percent

distribution by total births expected, by race and parity:

United States, 1982 and 1988 . . . . . . . . . . . . . . . . . . . . 23

8. Number of women 15–44 years of age and percent who

‘‘didn’t know’’ or who were ‘‘unsure’’ about their birth

expectations, by selected characteristics: United States,

1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

9. Number of unmarried women 15–44 years of age and

percent distribution by total births expected, according to

previous marital status and parity: United States, 1982 and

1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

10. Number of currently married women 15–44 years of age

and percent distribution by total births expected, according

to parity: United States, 1973, 1982, and 1988 . . . . . . . . 26

11. Number of National Survey of Family Growth sample

respondents who gave both a single number and a range

of additional expected births and weighted average

additional births expected per woman based on the

midpoint of the range, according to the single number:

United States, 1973 . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

12. Low and high estimates of average additional births

expected and average total births expected using the lower

and upper bounds of any given ranges, by race and age:

United States, 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

15

Symbols

- - - Data not available

. . . Category not applicable

− Quantity zero

0.0 Quantity more than zero but

less than 0.05

Z Quantity more than zero but

less than 500 where numbers

are rounded to thousands

* Figure does not meet standards

of reliability or precision

(see Technical notes)
Table 1. Total fertility rate and estimated completed cohort fertility for women 27 years of age, by year: United States, specified years,

1957–66 and each year 1969–90

Year

Total

fertility

rate1

Completed

cohort fertility,

women age 27

(and year of birth)2

1957 ................................................. 3.767 3.157 (1930)

1960 ................................................. 3.654 3.220 (1933)

1963 ................................................. 3.319 3.106 (1936)

1966 ................................................. 2.721 2.876 (1939)

1969 ................................................. 2.456 2.566 (1942)

1970 ................................................. 2.480 2.457 (1943)

1971 ................................................. 2.267 2.370 (1944)

1972 ................................................. 2.010 2.289 (1945)

1973 ................................................. 1.879 2.227 (1946)

1974 ................................................. 1.835 2.167 (1947)

1975 ................................................. 1.774 2.115 (1948)

1976 ................................................. 1.738 2.067 (1949)

1977 ................................................. 1.790 . . .

1978 ................................................. 1.760 . . .

1979 ................................................. 1.808 . . .

1980 ................................................. 1.840 . . .

1981 ................................................. 1.812 . . .

1982 ................................................. 1.828 . . .

1983 ................................................. 1.799 . . .

1984 ................................................. 1.807 . . .

1985 ................................................. 1.844 . . .

1986 ................................................. 1.838 . . .

1987 ................................................. 1.872 . . .

1988 ................................................. 1.934 . . .

1989 ................................................. 2.014 . . .

1990 ................................................. 2.081 . . .

1The total fertility rate is a measure of current fertility derived by summing the age-specific birth rates for a population of women of reproductive age in a given period. Data are from the Monthly

Vital Statistics Report and Vital Statistics of the United States (9,11,12).

2Completed cohort fertility is the average number of live births to a birth cohort of women upon completion of their childbearing, for example, at age 47. This information is available in the Vital

Statistics of the United States, table 1–19, for women who were born 1930–42 and age 27 in 1957–69 and age 47 or over as of January 1, 1989 (14–17). Completed cohort fertility was estimated

for women born 1943–49 who were age 27 in 1970–76 (ages 40–46 as of January 1, 1989) and for whom the average number of live births as of age 47 is not yet known. Estimates were made

by inflating the average number of live births as of January 1, 1989, to account for future childbearing. The estimates were based on the assumption that the percent of completed fertility that had

been achieved at each age was constant across cohorts of women. To estimate the completed fertility of women who were 27 in 1970, their average number of live births as of January 1, 1989,

(2.4574) was inflated by the ratio of the average number of live births at age 47 (2.5660) to the average number of live births at age 46 (2.5659) for women who were 1 year older (that is, women

who were 27 in 1969). Estimates for the remaining cohorts were made by deriving and applying a similar inflation factor based on the estimated completed lifetime fertility of the preceding cohort.

Cumulative birth rates for the cohorts born 1943–49 as of January 1, 1989, were 2.457, 2.369, 2.287, 2.223, 2.159, 2.101, and 2.044, respectively.

16
Table 2. Number of women 15–44 years of age and average number of children ever born, average additional births expected, and

average total births expected, by race and age: United States, 1982 and 1988

Race and age

1982 1988

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

All women1

15–44 years ............... 54,099 1.310 1.071 2.382 57,900 1.220 1.004 2.224

15–19 years .............. 9,521 0.097 2.228 2.330 9,179 0.083 2.072 2.155

20–24 years .............. 10,629 0.539 1.924 2.462 9,413 0.510 1.830 2.340

25–29 years .............. 10,263 1.215 1.000 2.215 10,796 1.092 1.242 2.334

30–34 years .............. 9,381 1.754 0.500 2.253 10,930 1.597 0.569 2.165

35–39 years .............. 7,893 2.211 0.147 2.359 9,583 1.933 0.195 2.128

40–44 years .............. 6,412 2.783 *0.027 2.810 7,999 2.163 0.050 2.213

White women

15–44 years ............... 45,367 1.271 1.089 2.362 47,076 1.197 1.008 2.205

15–19 years .............. 7,815 0.079 2.305 2.388 7,313 *0.059 2.171 2.230

20–24 years .............. 8,855 0.492 1.987 2,479 7,401 0.466 1.874 2.340

25–29 years .............. 8,569 1.152 1.033 2,184 8,672 1.029 1.263 2.292

30–34 years .............. 7,916 1.703 0.491 2,194 9,010 1.561 0.558 2.119

35–39 years .............. 6,697 2.168 0.145 2.313 7,936 1.885 0.179 2.064

40–44 years .............. 5,515 2.689 *0.021 2.709 6,745 2.154 *0.045 2.199

Black women

15–44 years ............... 6,985 1.598 0.952 2.553 7,679 1.418 0.819 2.237

15–19 years .............. 1,416 0.197 1.799 2.005 1,409 0.208 1.523 1.731

20–24 years .............. 1,472 0.851 1.491 2.342 1,364 0.858 1.374 2.232

25–29 years .............. 1,335 1.689 0.838 2.526 1,459 1.469 0.870 2.339

30–34 years .............. 1,144 2.142 0.490 2.631 1,406 1.819 0.509 2.328

35–39 years . . . . . . . . . . . . . . 884 2.595 0.193 2.798 1,170 2.314 0.201 2.514

40–44 years . . . . . . . . . . . . . . 734 3.586 0.081 3.667 872 2.315 *0.056 2.372

1All women include white, black, and other races. Other races not shown separately because of small sample size.

17
ied women 15–44 years of age and average number of children ever born, average additional births expected, and average total births expected, by

1973, 1982, and 1988

1973 1982 1988

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

. 30,009 2.240 0.815 2.804 34,935 1.903 0.571 2.474 36,842 1.769 0.547 2.317

. 1,074 0.515 1.925 2.351 682 *0.652 1.904 2.557 340 0.968 1.454 2.422. 5,339 0.984 1.493 2.325 4,818 0.924 1.500 2.423 3,631 0.917 1.480 2.397. 6,703 1.670 0.942 2.434 7,778 1.465 0.893 2.358 7,669 1.343 1.068 2.411. 5,979 2.578 0.448 2.871 8,218 1.878 0.431 2.309 9,220 1.789 0.497 2.286. 5,339 3.119 0.217 3.236 7,349 2.339 *0.110 2.448 8,581 2.068 0.153 2.220. 5,575 3.256 0.105 3.307 6,090 2.886 *0.022 2.908 7,401 2.295 *0.031 2.326

. 26,629 2.166 0.810 2.737 30,419 1.840 0.582 2.423 31,465 1.730 0.545 2.275. 959 0.471 1.947 2.340 622 *0.637 1.963 2.600 319 *0.966 1.494 2.460

. 4,767 0.933 1.514 2.305 4,353 0.893 1.510 2.403 3,176 0.890 1.494 2.385. 6,019 1.608 0.939 2.379 6,719 1.417 0.918 2.335 6,546 1.290 1.052 2.342. 5,301 2.516 0.428 2.799 7,099 1.821 0.419 2.240 7,824 1.752 0.488 2.240. 4,668 3.060 0.195 3.167 6,326 2.288 *0.107 2.395 7,277 2.024 *0.141 2.165. 4,916 3.152 0.088 3.197 5,300 2.788 *0.018 2.807 6,322 2.280 *0.031 2.311

. 3,047 2.922 0.833 3.404 3,440 2.493 0.478 2.971 3,614 2.109 0.439 2.548. 103 0.950 1.744 2.500 *39 *0.808 *1.266 *2.074 *21 *1.003 *0.825 *1.828. 547 1.423 1.272 2.473 388 1.352 1.224 2.576 322 1.230 1.295 2.525

. 618 2.274 0.937 2.944 777 1.981 0.733 2.714 695 1.711 0.792 2.503. 596 3.177 0.548 3.488 851 2.335 0.462 2.797 970 2.040 0.454 2.495. 573 3.822 0.346 3.958 737 2.828 *0.159 2.987 878 2.508 *0.172 2.680. 610 4.163 0.264 4.257 648 3.718 *0.060 3.778 728 2.518 *0.014 2.532

r races. Other races not shown separately because of small sample size.
orn 1938–73 and average children ever born, average additional births expected, and average total births expected, by race and year of birth:

1982 1988

Number of

women in

thousands Age

Average

children

ever born

Average

additional births

expected

Average

total births

expected

Number of

women in

thousands Age

Average

children

ever born

Average

additional births

expected

Average

total births

expected

. 253,831 - - - 1.302 1.076 2.379 256,690 - - - 1.197 1.025 2.222

. --- --- --- --- --- 3,750 15–17 0.022 2.071 2.093

. --- --- --- --- --- 5,805 18–20 0.136 2.070 2.206

. 4,816 15–17 0.029 2.259 2.298 5,586 21–23 0.424 1.864 2.288

. 6,933 18–20 0.184 2.264 2.449 6,124 24–26 0.764 1.695 2.459

. 6,302 21–23 0.549 1.937 2.486 6,296 27–29 1.085 1.198 2.283

. 5,875 24–26 0.932 1.257 2.189 6,652 30–32 1.480 0.741 2.221

. 6,265 27–29 1.336 0.887 2.223 6,510 33–35 1.668 0.451 2.120

. 5,589 30–32 1.645 0.611 2.257 5,881 36–38 1.919 0.236 2.155

. 5,673 33–35 1.916 0.306 2.222 5,379 39–41 2.074 0.087 2.160

. 4,554 36–38 2.261 0.143 2.405 4,709 42–44 2.113 *0.058 2.171

. 4,285 39–41 2.553 *0.073 2.626 - - - - - - - - - - - - - - -

. 3,539 42–44 2.848 *0.025 2.873 - - - - - - - - - - - - - - -

. 45,118 - - - 1.263 1.095 2.358 45,976 - - - 1.169 1.032 2.201

. --- --- --- --- --- 2,891 15–17 *0.007 2.151 2.159. --- --- --- --- --- 4,749 18–20 0.100 2.182 2.282. 3,866 15–17 *0.017 2.336 2.362 4,386 21–23 0.382 1.932 2.314

. 5,836 18–20 0.154 2.355 2.509 4,820 24–26 0.716 1.662 2.378

. 5,218 21–23 0.502 1.986 2.487 5,023 27–29 1.015 1.258 2.273

. 4,944 24–26 0.850 1.292 2.142 5,559 30–32 1.434 0.755 2.189

. 5,222 27–29 1.303 0.917 2.219 5,335 33–35 1.640 0.421 2.061

. 4,681 30–32 1.596 0.616 2.212 4,826 36–38 1.871 0.218 2.089

. 4,810 33–35 1.865 0.282 2.146 4,440 39–41 2.029 0.071 2.100

. 3,893 36–38 2.207 0.143 2.350 3,946 42–44 2.099 *0.060 2.159

. 3,643 39–41 2.531 *0.068 2.598 - - - - - - - - - - - - - - -

. 3,007 42–44 2.704 *0.020 2.724 - - - - - - - - - - - - - - -

. 6,966 - - - 1.595 0.955 2.553 7,596 - - - 1.412 0.828 2.239

. - - - - - - - - - - - - - - - 595 15–17 *0.073 1.622 1.695. - - - - - - - - - - - - - - - 861 18–20 0.343 1.438 1.782. 788 15–17 0.084 1.851 1.951 878 21–23 0.693 1.421 2.114. 919 18–20 0.390 1.719 2.109 769 24–26 1.234 1.215 2.449. 848 21–23 0.862 1.575 2.437 903 27–29 1.421 0.856 2.276. 861 24–26 1.395 1.085 2.480 827 30–32 1.828 0.573 2.401. 767 27–29 1.764 0.700 2.464 831 33–35 1.841 0.452 2.294. 699 30–32 2.045 0.557 2.602 747 36–38 2.282 0.267 2.549. 648 33–35 2.286 0.379 2.665 622 39–41 2.382 0.072 2.453. 495 36–38 2.657 0.164 2.840 563 42–44 2.339 *0.064 2.403. 499 39–41 2.849 0.130 2.978 - - - - - - - - - - - - - - -. 444 42–44 3.963 *0.059 4.022 - - - - - - - - - - - - - - -

r races. Other races not shown separately because of small sample size.

ble 1 because women who were 15 or 44 years old but were born after 1973 or before 1938 are excluded from this table.
ied women born 1929–73, and average children ever born, average additional births expected, and average total births expected, by race and year of

82, and 1988

1973 1982 1988

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

. 29,641 2.227 0.822 2.797 34,700 1.894 0.575 2.469 35,670 1.750 0.565 2.315

. - - - - - - - - - - - - - - - - - - - - - - - - *34 *0.280 *2.638 *2.918

. - - - - - - - - - - - - - - - - - - - - - - - - 373 *0.994 1.336 2.330

. - - - - - - - - - - - - 124 0.299 2.805 3.104 1,731 0.852 1.484 2.335. --- --- --- --- 1,109 0.612 1.826 2.438 3,538 1.078 1.448 2.526. --- --- --- --- 2,823 0.911 1.557 2.468 4,500 1.309 1.046 2.355

. 171 0.427 2.000 2.358 3,911 1.235 1.125 2.359 5,468 1.690 0.659 2.349. 1,460 0.586 1.864 2.375 5,127 1.520 0.805 2.324 5,593 1.841 0.388 2.228. 3,072 0.909 1.545 2.313 4,878 1.818 0.543 2.360 5,229 2.056 0.186 2.242. 4,127 1.318 1.176 2.334 5,037 2.010 0.255 2.265 4,918 2.209 0.056 2.265. 3,906 1.809 0.849 2.471 4,235 2.382 0.116 2.498 4,285 2.266 *0.035 2.301. 3,801 2.380 0.567 2.763 4,106 2.631 0.037 2.668 - - - - - - - - - - - -. 3,240 2.801 0.286 2.980 3,349 2.968 0.024 2.993 - - - - - - - - - - - -. 3,217 3.102 0.258 3.240 - - - - - - - - - - - - - - - - - - - - - - - -. 3,322 3.198 0.140 3.273 - - - - - - - - - - - - - - - - - - - - - - - -. 3,325 3.325 0.091 3.367 - - - - - - - - - - - - - - - - - - - - - - - -

. 26,290 2.153 0.817 2.730 30,194 1.830 0.586 2.417 30,393 1.706 0.564 2.270

. - - - - - - - - - - - - - - - - - - - - - - - - *34 *0.280 *2.638 *2.918

. - - - - - - - - - - - - - - - - - - - - - - - - 353 *0.993 1.366 2.359

. - - - - - - - - - - - - 118 *0.302 *2.831 *3.133 1,480 0.847 1.507 2.354

. --- --- --- --- 1,021 0.595 1.876 2.471 3,072 1.020 1.404 2.424. --- --- --- --- 2,532 0.890 1.553 2.443 3,815 1.256 1.059 2.315

. 160 0.397 2.030 2.376 3,444 1.156 1.157 2.313 4,742 1.645 0.665 2.310. 1,294 0.528 1.874 2.339 4,452 1.497 0.825 2.322 4,722 1.804 0.367 2.171. 2,725 0.845 1.592 2.307 4,184 1.769 0.531 2.300 4,390 2.017 0.170 2.187. 3,718 1.271 1.164 2.292 4,367 1.940 0.239 2.179 4,150 2.157 0.050 2.207. 3,512 1.746 0.853 2.415 3,670 2.331 0.115 2.445 3,634 2.254 *0.040 2.294. 3,369 2.336 0.540 2.707 3,528 2.600 0.034 2.634 - - - - - - - - - - - -. 2,892 2.717 0.271 2.887 2,878 2.823 0.021 2.844 - - - - - - - - - - - -. 2,789 3.068 0.226 3.191 - - - - - - - - - - - - - - - - - - - - - - - -. 2,911 3.126 0.125 3.194 - - - - - - - - - - - - - - - - - - - - - - - -. 2,920 3.188 0.075 3.224 - - - - - - - - - - - - - - - - - - - - - - - -
ied women born 1929–73, and average children ever born, average additional births expected, and average total births expected, by race and year of

82, and 1988—Con.

1973 1982 1988

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

. 3,018 2.907 0.839 3.394 3,430 2.490 0.479 2.969 3,541 2.108 0.448 2.557

. - - - - - - - - - - - - - - - - - - - - - - - - *– *– *– *–. - - - - - - - - - - - - - - - - - - - - - - - - *21 *1.003 *0.825 *1.828

. - - - - - - - - - - - - *3 *0.403 *1.791 *2.194 184 0.993 1.188 2.181

. - - - - - - - - - - - - 64 0.785 1.240 2.025 283 1.570 1.133 2.703

. - - - - - - - - - - - - 219 1.294 1.343 2.637 432 1.603 0.862 2.465. *11 *0.858 *1.498 *2.098 415 1.870 0.927 2.796 520 2.101 0.499 2.601. 154 1.095 1.787 2.711 473 1.932 0.666 2.597 584 2.059 0.409 2.468. 327 1.398 1.122 2.327 521 2.247 0.540 2.787 553 2.478 0.227 2.704. 391 1.792 1.260 2.715 498 2.496 0.347 2.844 498 2.591 *0.063 2.654. 352 2.435 0.761 2.997 399 2.875 0.140 3.016 466 2.511 *0.005 2.516. 382 2.856 0.725 3.269 434 3.061 0.077 3.138 - - - - - - - - - - - -. 301 3.617 0.351 3.810 402 4.032 0.050 4.082 - - - - - - - - - - - -. 366 3.629 0.362 3.782 - - - - - - - - - - - - - - - - - - - - - - - -. 356 3.923 0.367 4.053 - - - - - - - - - - - - - - - - - - - - - - - -. 380 4.425 0.207 4.497 - - - - - - - - - - - - - - - - - - - - - - - -

r races. Other races not shown separately because of small sample size.
ied women born 1929–73 who were first married prior to the National Survey of Family Growth Cycle I (1973) and average children ever born, average

nd average total births expected, by race and year of birth: United States, 1973, 1982, and 1988

1973 19821 19881

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

Number of

women in

thousands

Average

children

ever born

Average

additional

births

expected

Average

total

births

expected

. 29,641 2.227 0.822 2.797 14,979 2.510 *0.124 2.634 13,429 2.341 *0.070 2.411. 1,460 0.586 1.864 2.375 1,192 2.070 *0.347 2.417 1,694 2.267 *0.166 2.434

. 3,072 0.909 1.545 2.313 2,093 2.201 *0.333 2.534 3,374 2.342 *0.088 2.430

. 4,127 1.318 1.176 2.334 2,862 2.238 *0.140 2.378 4,071 2.364 *0.035 2.399

. 3,906 1.809 0.849 2.471 2,993 2.489 *0.070 2.559 4,009 2.331 *0.032 2.362

. 3,801 2.380 0.567 2.763 3,166 2.753 *0.019 2.771 - - - - - - - - - - - -

. 3,240 2.801 0.286 2.980 2,522 3.015 *0.015 3.030 - - - - - - - - - - - -

. 26,290 2.153 0.817 2.730 13,418 2.477 *0.125 2.602 11,627 2.298 *0.070 2.367. 1,294 0.528 1.874 2.339 1,087 2.070 *0.350 2.420 1,455 2.194 *0.162 2.356

. 2,725 0.845 1.592 2.307 1,889 2.153 *0.343 2.495 2,935 2.301 *0.083 2.384

. 3,718 1.271 1.164 2.292 2,557 2.215 *0.132 2.347 3,531 2.317 *0.035 2.352

. 3,512 1.746 0.853 2.415 2,634 2.450 *0.070 2.520 3,456 2.302 *0.037 2.339

. 3,369 2.336 0.540 2.707 2,860 2.761 *0.017 2.778 - - - - - - - - - - - -

. 2,892 2.717 0.271 2.887 2,251 2.929 *0.014 2.943 - - - - - - - - - - - -

. 3,018 2.907 0.839 3.394 1,059 3.015 *0.155 3.170 1,338 2.692 *0.070 2.762

. 391 1.792 1.260 2.715 *197 *2.516 *0.222 *2.739 379 2.712 *0.055 2.767

. 352 2.435 0.761 2.997 *215 *3.013 *0.112 *3.125 418 2.651 – 2.651

are included in the analysis if their first marriage occurred in or before September 1973, the midpoint of interviewing in Cycle I.

races. Other races not shown separately because of small sample size.
5–44 years of age and percent distribution by total births expected, by race and parity: United States, 1982 and 1988

1988 1982

Number of

women in

thousands Total

Total births expected

Number of

women in

thousands Total

Total births expected

0123

4 and

over 0123

4 and

over

. 57,900 100.0 8.7 14.2 44.3 21.5 11.3 54,099 100.0 7.4 12.1 43.1 23.2 14.3

. 25,129 100.0 20.1 14.3 44.6 14.1 6.9 22,941 100.0 17.5 13.1 44.4 16.1 8.9. 9,906 100.0 . . . 46.7 37.8 12.3 3.1 8,979 100.0 . . . 39.3 44.0 12.3 4.4. 13,237 100.0 . . . . . . 80.9 15.1 4.0 11,645 100.0 . . . . . . 78.7 16.6 4.7. 6,188 100.0 . . . . . . . . . 91.2 8.8 6,499 100.0 . . . . . . . . . 88.9 11.1

. 3,440 100.0 . . . . . . . . . . . . 100.0 4,035 100.0 . . . . . . . . . . . . 100.0

. 47,076 100.0 9.2 13.6 44.6 22.0 10.7 45,367 100.0 7.5 11.8 43.9 23.2 13.6

. 20,769 100.0 20.8 13.3 44.3 14.8 6.8 19,720 100.0 17.3 12.5 44.6 16.4 9.2. 7,720 100.0 . . . 47.0 37.2 12.4 3.4 7,191 100.0 . . . 40.3 43.2 12.0 4.5. 10,942 100.0 . . . . . . 81.5 14.7 3.8 9,963 100.0 . . . . . . 80.2 15.6 4.1. 5,110 100.0 . . . . . . . . . 92.1 7.9 5,417 100.0 . . . . . . . . . 89.7 10.3

. 2,535 100.0 . . . . . . . . . . . . 100.0 3,076 100.0 . . . . . . . . . . . . 100.0

. 7,679 100.0 7.7 18.7 41.7 18.1 13.8 6,985 100.0 6.3 13.8 38.1 21.9 19.9

. 2,825 100.0 20.9 21.4 46.1 7.3 4.2 2,447 100.0 18.0 18.2 43.7 13.6 6.5. 1,695 100.0 . . . 48.9 38.1 10.9 *2.0 1,459 100.0 . . . 35.5 47.3 12.3 4.9. 1,608 100.0 . . . . . . 78.1 16.6 5.3 1,358 100.0 . . . . . . 66.5 24.1 9.4. 820 100.0 . . . . . . . . . 89.1 10.9 826 100.0 . . . . . . . . . 83.2 16.8

. 731 100.0 . . . . . . . . . . . . 100.0 894 100.0 . . . . . . . . . . . . 100.0

r races. Other races not shown separately because of small sample size.
5–44 years of age and percent who ‘‘didn’t know’’ or who were ‘‘unsure’’ about their birth expectations, by selected characteristics:

Total

Currently

married

Not currently

married

Total

Percent

didn’t

know1

Percent

unsure2 Total

Percent

didn’t

know1

Percent

unsure2 Total

Percent

didn’t

know1

Percent

unsure2

. 57,900 6.4 25.1 29,147 6.0 15.5 28,753 6.9 34.7

. 47,076 6.4 24.2 25,426 5.8 14.8 21,650 7.1 35.1

. 7,679 5.9 28.0 2,197 6.7 18.2 5,482 5.7 31.9

. 9,179 4.3 46.5 312 *1.6 21.4 8,867 4.4 47.4. 9,413 5.2 35.7 3,025 6.0 31.6 6,388 4.8 37.7. 10,796 9.0 29.2 6,286 8.7 21.8 4,510 9.4 39.6

. 10,930 9.7 20.0 7,361 8.3 16.6 3,569 12.5 27.3

. 9,583 6.3 11.8 6,444 4.9 10.6 3,139 9.1 14.5. 7,999 2.7 5.1 5,719 *1.7 3.9 2,280 5.5 8.3

. 25,129 6.5 38.6 5,533 6.6 25.2 19,596 6.5 42.4. 9,906 9.2 24.3 6,218 9.1 22.4 3,688 9.3 27.6. 13,237 5.8 12.3 10,246 5.6 11.6 2,991 6.6 15.0

. 9,628 4.2 7.9 7,150 3.5 7.4 2,478 6.4 9.4

that they didn’t know whether they intended to have a(nother) baby (appendix III, question D-25), or if they did intend to have a(nother) baby, they responded that they didn’t know how many (appendix III, question

‘yes’’ or ‘‘no’’ regarding their intention to have a(nother) baby (appendix III, question D-25), and initially gave a number or range of births they expected to have (appendix III, question D-26), but then when

‘not very sure’’ about their response (appendix III, question D-27).

er races. Other races not shown separately because of small sample size.
d women 15–44 years of age and percent distribution by total births expected, according to previous marital status and parity: United States,

1988 1982

Number of

women in

thousands Total

Total births expected

Number of

women in

thousands Total

Total births expected

0123

4 and

over 0 1 2 3

4 and

over

. 28,753 100.0 12.1 16.8 42.5 18.0 10.6 25,868 100.0 10.0 14.3 43.6 18.6 13.4

. 19,596 100.0 17.8 14.0 45.0 15.3 7.8 17,843 100.0 14.5 13.0 44.9 17.2 10.4. 3,688 100.0 . . . 56.5 30.6 10.5 *2.4 3,088 100.0 . . . 45.1 39.6 10.7 *4.6. 2,991 100.0 . . . . . . 75.9 18.2 5.9 2,603 100.0 . . . . . . 79.0 13.7 *7.4. 1,407 100.0 . . . . . . . . . 88.0 12.0 1,194 100.0 . . . . . . . . . 87.3 *12.7

. 1,071 100.0 . . . . . . . . . . . . 100.0 1,139 100.0 . . . . . . . . . . . . 100.0

. 7,695 100.0 11.5 21.2 33.4 20.3 13.6 6,704 100.0 *6.1 19.2 37.5 19.0 18.2

. 1,628 100.0 54.5 15.3 20.2 6.9 *3.0 1,148 100.0 35.4 *27.1 *26.5 *6.5 *4.6. 1,946 100.0 . . . 71.0 22.2 6.1 *0.6 1,667 100.0 . . . 58.5 30.8 *7.4 *3.3. 2,238 100.0 . . . . . . 80.6 16.1 *3.3 1,997 100.0 . . . . . . 85.0 *9.6 *5.4. 1,088 100.0 . . . . . . . . . 89.6 10.4 977 100.0 . . . . . . . . . 90.6 *9.4

. 797 100.0 . . . . . . . . . . . . 100.0 915 100.0 . . . . . . . . . . . . 100.0

. 21,058 100.0 12.4 15.2 45.8 17.1 9.5 19,164 100.0 11.4 12.6 45.8 18.4 11.8

. 17,968 100.0 14.5 13.9 47.2 16.1 8.3 16,695 100.0 13.1 12.0 46.1 18.0 10.8. 1,742 100.0 . . . 40.3 39.8 15.4 *4.4 1,422 100.0 . . . 29.4 49.9 14.5 *6.2. 754 100.0 . . . . . . 61.9 24.7 *13.4 606 100.0 . . . . . . 59.1 27.1 *13.8

. 594 100.0 . . . . . . . . . 44.3 55.7 441 100.0 . . . . . . . . . 35.6 64.4
Table 10. Number of currently married women 15–44 years of age and percent distribution by total births expected, according to parity:

United States, 1973, 1982, and 1988

Year and parity

Number of

women in

thousands Total

Total births expected

0123

4 and

over

1988:

Total .................... 29,147 100.0 5.3 11.6 46.2 24.9 12.0

0 ..................... 5,533 100.0 28.0 15.1 43.4 10.0 3.5

1 ..................... 6,218 100.0 . . . 41.0 42.2 13.4 3.4

2 ..................... 10,246 100.0 . . . . . . 82.3 14.2 3.5

3 ..................... 4,781 100.0 . . . . . . . . . 92.1 7.9

4 and over ............... 2,369 100.0 . . . . . . . . . . . . 100.0

1982:

Total .................... 28,231 100.0 5.0 10.0 42.5 27.4 15.1

0 ..................... 5,098 100.0 27.7 13.8 42.6 12.4 *3.6

1 ..................... 5,891 100.0 . . . 36.2 46.3 13.2 *4.2

2 ..................... 9,042 100.0 . . . . . . 78.6 17.4 *4.0

3 ..................... 5,305 100.0 . . . . . . . . . 89.3 10.7

4 and over ............... 2,896 100.0 . . . . . . . . . . . . 100.0

1973:

Total .................... 26,240 100.0 3.5 9.0 40.0 24.8 22.6

0 ..................... 4,689 100.0 19.8 14.2 51.4 10.3 4.3

1 ..................... 5,000 100.0 . . . 34.0 50.9 11.5 3.7

2 ..................... 7,054 100.0 . . . . . . 78.7 16.3 5.0

3 ..................... 4,723 100.0 . . . . . . . . . 91.3 8.7

4 and over ............... 4,773 100.0 . . . . . . . . . . . . 100.0

Table 11. Number of National Survey of Family Growth sample respondents who gave both a single number and a range of additional

expected births and weighted average additional births expected per woman, based on the midpoint of the range, according to the

single number: United States, 1973

Age group

Number of

sample women

Average additional births

expected per range1

Average additional births

expected per number2

15–44 years ...................... 1,143 1.631 1.724

15–19 years . . . . . . . . . . . . . . . . . . . . . 145 2.197 2.252

20–24 years . . . . . . . . . . . . . . . . . . . . . 420 1.858 1.887

25–29 years . . . . . . . . . . . . . . . . . . . . . 304 1.452 1.589

30–34 years . . . . . . . . . . . . . . . . . . . . . 166 1.232 1.391

35–39 years . . . . . . . . . . . . . . . . . . . . . 76 1.227 1.342

40–44 years . . . . . . . . . . . . . . . . . . . . . 32 1.212 1.456

1Averages are calculated based on the midpoint of the range of additional births expected.

2Averages are calculated based on the point estimate of additional births expected.

26
Table 12. Low and high estimates of average additional births expected and average total births expected using the lower and upper

bounds of any given ranges, by race and age: United States, 1988

Age and race

Low1 High2

Average

additional births

expected

Average

total births

expected

Average

additional births

expected

Average

total births

expected

All races

Total3 .......................... 0.964 2.184 1.044 2.264

15–19 years ...................... 1.984 2.067 2.160 2.243

20–24 years ...................... 1.754 2.264 1.907 2.416

25–29 years ...................... 1.194 2.286 1.289 2.382

30–34 years ...................... 0.549 2.146 0.589 2.185

35–39 years ...................... 0.192 2.124 0.199 2.131

40–44 years ...................... 0.049 2.212 0.050 2.214

White women

Total ........................... 0.966 2.163 1.050 2.247

15–19 years ...................... 2.067 2.126 2.275 2.334

20–24 years ...................... 1.795 2.261 1.953 2.419

25–29 years ...................... 1.213 2.242 1.313 2.342

30–34 years ...................... 0.541 2.102 0.574 2.136

35–39 years ...................... 0.175 2.060 0.183 2.068

40–44 years ...................... *0.044 2.198 *0.046 2.200

Black women

Total ........................... 0.803 2.221 0.835 2.253

15–19 years ...................... 1.503 1.711 1.544 1.752

20–24 years ...................... 1.338 2.195 1.410 2.268

25–29 years ...................... 0.847 2.316 0.892 2.361

30–34 years ...................... 0.504 2.322 0.514 2.333

35–39 years ...................... 0.199 2.513 0.203 2.516

40–44 years ...................... *0.056 2.372 *0.056 2.372

1Low estimates are derived from the number of children ever born and the number of additional births expected, or in cases where a range was given, the lower bound of the range.

2High estimates are derived from the number of children ever born and the number of additional births expected, or in cases where a range was given, the upper bound of the range.

3Total includes white, black, and other races. Other races not shown separately because of small sample size.

NOTE: The base populations for these rates appear in table 2.

27
Appendixes

Contents

I. Technical notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Statistical design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Measurement process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Data reduction and quality control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Reliability of estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

II. Definition of terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

III. Items on the 1988 National Survey of Family Growth questionnaire related to birth expectations. . . . . . . . . . . . . . . . . . 35

Appendix tables

I. Estimated standard error parameters for percentages of total or total nonblack women and black women: 1988 . . . . . . 31

II. Approximate relative standard errors and standard errors for estimated number of total or nonblack women:

National Survey of Family Growth, 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

III. Approximate relative standard errors and standard errors for estimated number of black women: National Survey

of Family Growth, 1988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

IV. Estimated standard errors of percents of total or total nonblack women: National Survey of Family Growth, 1988. . . . 31

V. Estimated standard errors of the ratio of total births expected per 1,000 women: National Survey of Family

Growth, 1988. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

VI. Estimated standard errors of the ratio of total births expected per 1,000 black women: National Survey of Family

Growth, 1988. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

VII. Estimates of standard errors of percents of total or total nonblack women: National Survey of Family

Growth, 1982. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

VIII. Estimated standard errors of the ratio of total births expected per 1,000 women: National Survey of Family

Growth, 1982. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

IX. Estimated standard errors of the ratio of total births expected per 1,000 black women: National Survey of Family

Growth, 1982. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

X. Estimated standard errors of the ratio of total births expected per 1,000 women: National Survey of Family

Growth, 1973. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

28
Appendix I

Technical notes

Background

This report is one of a series based on the National Survey

of Family Growth (NSFG), conducted by the National Center

for Health Statistics (NCHS). The NSFG was designed to

provide data on fertility, contraception, infertility, and other

aspects of maternal and infant health related to childbearing.

The NSFG is a periodic survey based on personal interviews with a nationwide sample of women. The NSFG has

been conducted four times—in 1973, 1976, 1982, and 1988.

The present report is based on Cycles I, III, and IV of the

NSFG. Interviewing for Cycle I was conducted in 1973 under

contract by the National Opinion Research Center. Interviewing for Cycles II, III, and IV was conducted under contract by

Westat, Inc., in 1976, 1982, and 1988, respectively.

For Cycle IV, personal (face-to-face) interviews were

conducted between January and August 1988, with a national

sample of 8,450 women who were 15–44 years of age as of

March 15, 1988, in the civilian noninstitutionalized population

of the United States. (For the first time in 1988, Alaska and

Hawaii were included in the sample.) In 1982, interviews were

conducted with 7,969 women 15–44 years of age from the

civilian noninstitutionalized population of the conterminous

United States. In 1973, interviews were conducted with 9,797

women 15–44 years of age who were currently married or

previously married. The only never-married women included

in 1973 were the small proportion who had children of their

own living with them. A detailed report on Cycle IV is

contained in reference 21. A detailed description of the

methods and procedures used for previous NSFG cycles can

be found in references 24–26. This appendix presents a

summary of the more important technical aspects of the 1988

NSFG.

In Cycle IV, interviews were conducted with 8,450 women,

including 2,771 black women, 5,354 white women, and 325

women of other races. The interviews were conducted by

trained female interviewers in respondents’ homes and lasted

an average of 70 minutes. The interview focused on the

woman’s pregnancy history; her past and current use of

contraceptives; her physical ability to bear children (including

surgical sterilization and infertility); expectations for having

children in the future; use of medical services for birth control,

infertility, and prenatal care; and a wide range of social,

economic, and demographic characteristics.

Statistical design

The NSFG is based on a multistage area probability

sample. Black households were sampled at higher rates than

other households so that reliable estimates of statistics could

be presented separately for black women. In addition, the

sample was designed to provide reliable estimates for each of

the four major geographic regions of the United States. The

sample was not large enough to produce estimates for individual States, counties, or other local areas.

The 8,450 women interviewed for the 1988 NSFG were

drawn from households in which someone had already been

interviewed for another NCHS survey, the National Health

Interview Survey (NHIS), between October 1985 and March

1987. The NHIS is a continuous survey of the civilian

noninstitutionalized population of the United States in which

data are collected for each household member on disabilities,

health conditions, doctor visits, hospitalizations, and other

health-related topics.

NCHS provided computer files to Westat, Inc., of households that participated in the NHIS, along with information on

addresses and household composition. Households were

included if a member had been interviewed between October

1985 and March 1987, inclusively. Westat, Inc., selected the

NSFG sample of households from 156 of the 198 primary

sampling units (PSU’s) in the NHIS design. (A PSU is a

county or group of contiguous counties. The sampled PSU’s

were located in nearly every State and included all of the

largest metropolitan areas in the United States, as determined

by the 1980 Census.) In comparison, Cycle III was confined to

79 PSU’s. The increased dispersion of the sample resulted in

smaller sampling errors in 1988 than in 1982.

The first step was to select households, and the second

was to select women from those households. No more than

one woman was selected per household. Within each selected

household, all eligible women had an equal probability of

selection for the NSFG. Interviewers were trained to trace the

woman to her new address if she had moved since her

household’s participation in the NHIS. After locating a sampled

woman, the interviewer conducted a brief ‘‘screener’’ interview to ascertain that she was indeed eligible for the NSFG.

The NSFG is designed to provide national estimates of

the number of women with particular characteristics—for

example, the number using oral contraceptives or the number

29
who are infertile. In order to make such estimates, each

sample case (woman) must be assigned a ‘‘sampling weight,’’

simply a multiplier that is the number of women in the

population that she represents. In the 1988 NSFG, the final

weights ranged from 197 to 54,997 and averaged about 6,852.

They were derived by using four basic steps:

+ Inflation by the reciprocal of the probability of selection—

The probability of selection is the product of the probabilities of selection of the PSU, segment, household, and

sample person within the household. This weight is called

the baseweight, or W0. For example, if the probability of

selection is 1 in 5,000, then W0 is 5,000.

+ Trimming—About 100 cases in the 1988 NSFG had

extremely large baseweights (largest W0 was greater than

50,000). In previous cycles, these large weights were left

alone but they could have large effects on estimates,

particularly among smaller categories of variables. To

reduce this problem, these large baseweights in Cycle IV

were trimmed to a maximum value of 8,000 for black

women (about four times the average W0 for black women)

and 19,000 for women who were not black (about three

times their average W0). The trimmed weight is called W1.

Trimming reduced the total weighted numbers to less than

the 57.9 million U.S. women who were known to be

15–44 years of age in 1988. These W1 weights underwent

up to two more iterations of trimming to yield the reduced,

trimmed weights (W3).

+ Nonresponse adjustment—For Cycle IV, 51 nonresponse

adjustment cells were identified, based on extensive analysis of response rates using variables available from the

NHIS (15). The trimmed weights were adjusted for nonresponse using the cell-specific ratio of the weighted sum

of all cases to the weighted sum of all completed cases

(ratio-adjusted). These new weights were called ‘‘nonresponse adjusted weights’’ (W4).

+ Post-stratification by marital status, age, parity, and race—

The weights were then ratio-adjusted within each of a

74-cell matrix of categories of age (15–17, 18–19, 20–24,

25–29, 30–34, 35–39, 40–44), by race (black versus

nonblack), by marital status (ever-married versus nevermarried), and by parity (0, 1, 2, 3, 4 and over). The control

totals for each of these 74 cells were obtained from the

June 1988 Current Population Survey (CPS), conducted

by the U.S. Bureau of the Census.

The effect of this ratio adjustment process was to make

the sample more closely representative of the civilian noninstitutionalized population of women 15–44 years of age in the

United States. The final ‘‘post-stratification’’ yielded weights

(W5), which reduced the sample variances of the estimates for

most statistics.

Estimates of weighted numbers shown in the tables of this

report were rounded to the nearest thousand. Aggregate weights

and percents may not add to the total because of this rounding.

Measurement process

Field operations for Cycle IV were carried out by Westat,

Inc., under contract with NCHS; these operations included

interviewing a few hundred women in a practice survey, called

a ‘‘Pretest’’; selecting the sample; interviewing women in the

main survey; and performing specified quality control checks

on the completed questionnaires. Interviewers, all of whom

were female, were trained for 1 week before field work. The

first five interviews completed by each interviewer were

reviewed; after a high level of quality was achieved by an

interviewer, this review was reduced to a sample of questionnaires, unless an unacceptable level of error was found. A

10-percent sample of respondents were recontacted by telephone to verify that the interview had taken place and that

certain key items had been accurately recorded.

A portion of the questionnaire used for this report is

reproduced in appendix III. Two forms of the questionnaire

were used, one for women 15–24 years of age and one for

women 25–44. The questionnaire for women 15–24 included a

few additional items that referred to early experiences that

women over 25 could not be expected to remember accurately.

Data reduction and quality control

The responses of each woman to the interview questions

were translated into predetermined numerical codes (that is,

they were coded) and these code numbers were recorded on

computer tapes (that is, they were keyed). The first few

questionnaires coded by each coder were checked completely;

after an acceptable level of quality was reached, verification of

coding was performed on a systematic sample of each coder’s

questionnaires. The data were edited by computer to identify

inconsistencies between responses as well as code numbers

not allowed in the coding scheme; these errors were corrected.

Missing data on the variables used in this report were

imputed to provide consistent national estimates. (To speed

release of the public-use computer tape, however, not all

variables on the computer tape were imputed.)

Reliability of estimates

Because the statistics presented in this report are based on

a sample, they may differ somewhat from the figures that

would have been obtained had a complete census been taken

using the same questionnaires, instructions, interviewing personnel, and field procedures. This chance difference between

sample results and a complete count is referred to as sampling

error.

Sampling error is measured by a statistic called the

standard error of estimate. The chances are about 68 in 100

that an estimate from the sample will differ from a complete

count by less than the standard error. The chances are about 95

in 100 that the difference between the sample estimate and a

complete count will be less than twice the standard error. The

relative standard error (RSE), or coefficient of variation, of an

estimate is obtained by dividing the standard error of the

estimate by the estimate itself and is expressed as a percent of

the estimate. Percents that have a relative standard error of

more than 30 percent are considered unreliable.

30
Estimation of standard errors

Because of the complex multistage design of the NSFG

sample, conventional formulas for calculating sampling errors

are inapplicable. Standard errors were, therefore, estimated

empirically by using a technique known as balanced halfsample replication. This technique produces highly reliable,

unbiased estimates of sampling errors. Its application to the

NSFG has been described elsewhere (21).

Because it would be prohibitively expensive and cumbersome to estimate and publish a standard error for each percent

or other statistic by this technique, standard errors were

computed for selected statistics and population subgroups that

were chosen to represent a wide variety of demographic

characteristics and a wide variation in the size of the estimates

themselves. Curves were then fitted to the RSE estimates

(ratio of the standard error to the estimate itself) for numbers

of women according to the model

RSE (N')=(A + B/N')

1/2

where N' is the number of women and A and B are the

parameters whose estimates determine the shape of the curve.

Separate curves were fitted for women of all races combined

and nonblack women and for black women, because a different sampling rate was used for black women. Selected estimates of A and B are shown in table I.

To calculate the estimated standard error or RSE of an

aggregate or percent, the appropriate estimates of A and B are

used in the equations:

RSEN' = (A + B/N')

1/2

SEN' = (A + B/N')

1/2 (N')

RSEP' = {[(B/P') (100–P')]/ X') }1/2

SEP' = {[(B*P') (100–P')]/ X') }1/2

where

N' = number of women

P' = percent

X' = number of women in denominator of percent

SE = standard error

RSE = relative standard error

Tables II–X show some illustrative standard errors of

aggregates, percents, and rates for women from Cycles I, III,

and IV of the NSFG.

Testing differences

The standard error of a difference between two comparative statistics, such as the proportion of white women expecting no births compared with the proportion of black women

expecting no births, is approximately the square root of the

sum of the squares of the standard errors of the statistics

considered separately, or calculated by the formula: if

d = P'

1 – P'2

then

Sd = √[(P'

1)

2 (RSEp'1)2 + (P'

2)

2 (RSEp'2)2

]

where P'

1 is the estimated percent for one group and P'2 is the

estimated percent for the other group, and RSEp'

1 and RSEp'2

are the relative standard errors of P'

1 and P'2. This formula

will represent the actual standard error quite accurately for the

difference between separate and uncorrelated characteristics,

although it is only an approximation in most other cases.

Table I. Estimated standard error parameters for percentages of

total or total nonblack women and black women: 1988

Characteristic

Estimated parameters

a b

All races and total nonblack .... –0.00018 10,738

Black .................. –0.000626 5,181

Table II. Approximate relative standard errors and standard

errors for estimated number of total or nonblack women:

National Survey of Family Growth, 1988

Size of estimate

Relative standard

error in percent

Standard

error

100,000 ............... 32.0 32,000

250,000 ............... 20.4 51,000

500,000 ............... 14.4 72,000

1,000,000 .............. 10.2 102,000

5,000,000 . . . . . . . . . . . . . . 4.4 221,000

10,000,000 . . . . . . . . . . . . . 3.0 298,000

20,000,000 . . . . . . . . . . . . . 1.9 377,000

30,000,000 . . . . . . . . . . . . . 1.3 400,000

50,000,000 . . . . . . . . . . . . . 0.6 294,000

58,000,000 . . . . . . . . . . . . . 0.2 131,000

Table III. Approximate relative standard errors and standard

errors for estimated number of black women: National Survey of

Family Growth, 1988

Size of estimate

Relative standard

error in percent

Standard

error

100,000 ............... 22.0 22,000

250,000 ............... 14.0 35,000

500,000 . . . . . . . . . . . . . . . 9.8 49,000

1,000,000 . . . . . . . . . . . . . . 6.7 67,000

5,000,000 . . . . . . . . . . . . . . 2.0 101,000

7,500,000 . . . . . . . . . . . . . . 0.8 60,000

Table IV. Estimated standard errors of percents of total or total

nonblack women: National Survey of Family Growth, 1988

Base of percent

Estimated percent

2 or

98

5 or

95

10 or

90

20 or

80

30 or

70

40 or

60 50

Standard error in percentage points

100,000 . . . . . . . . . 4.6 7.1 9.8 13.1 15.0 16.1 16.4

500,000 . . . . . . . . . 2.1 3.2 4.4 5.9 6.7 7.2 7.3

1,000,000 . . . . . . . . 1.5 2.3 3.1 4.1 4.7 5.1 5.2

5,000,000 . . . . . . . . 0.6 1.0 1.4 1.9 2.1 2.3 2.3

10,000,000 . . . . . . . 0.5 0.7 1.0 1.3 1.5 1.6 1.6

30,000,000 . . . . . . . 0.3 0.4 0.6 0.8 0.9 0.9 0.9

50,000,000 . . . . . . . 0.2 0.3 0.4 0.6 0.7 0.7 0.7

58,000,000 . . . . . . . 0.2 0.3 0.4 0.5 0.6 0.7 0.7

31
A difference among comparable proportions or other

statistics from two or more subgroups is considered to be

statistically significant when a difference of that size or larger

would be expected by chance in fewer than 5 percent of

repeated samples of the same size and type, if no true

difference existed in the populations sampled (also known as

type I error or α level). Such a difference would be statistically

significant at the 0.05 level. By this criterion, if the observed

difference or a larger one could be expected by chance in more

than 5 percent of repeated samples, then one cannot be

sufficiently confident to conclude that a real difference exists

between the populations. When an observed difference is large

enough to be statistically significant, the true difference in the

population is estimated to lie between the observed difference

plus or minus two standard errors of that difference in 95 of

100 samples.

Although the 5-percent criterion is conventionally applied,

it is in a sense arbitrary; depending on the purpose of the

particular comparison, a different level of significance may be

more useful. For greater confidence, one would test for

significance at the 0.01 (1 percent) level, but if one can accept

a 10-percent chance of concluding a difference exists when

there actually is none in the population, a test of significance

at the 10-percent level would be appropriate.

The term ‘‘similar,’’ as used in this report, means that any

observed difference between two estimates being compared is

not statistically significant, but terms such as ‘‘greater,’’ ‘‘less,’’

‘‘larger,’’ and ‘‘smaller’’ indicate that the observed differences

are statistically significant at the 0.05 level using a two-tailed

normal deviate test (z-test) with 39 degrees of freedom.

Statements about differences that are qualified in some way (as

by the phrases ‘‘the data suggest’’ and ‘‘some evidence’’)

indicate that the difference is significant at the 0.10 level but

not at the 0.05 level.

When a substantial difference that is observed is found not

to be statistically significant, one should not conclude that no

difference exists but simply that such a difference cannot be

established with 95-percent confidence from this sample. This

is especially important for estimates based on smaller subgroups of women, such as Hispanic women or teenagers.

Furthermore, lack of comment in the text about any two

statistics does not mean that the difference was tested and

found not to be significant.

The number of replicates in the balanced half-sample

replication design minus one (99 in Cycle IV) can reasonably

be used as an estimate of the number of degrees of freedom.

For example, in 1988, 16.4 percent of white women and

22.1 percent of black women had had just one live birth. To

Table V. Estimated standard errors of the ratio of total births

expected per 1,000 women: National Survey of Family Growth,

1988

Base of ratio

Estimated ratio

1,000 2,000 3,000 4,000 5,000

100,000 . . . . . . . . . . . . . 407 576 705 814 910

200,000 . . . . . . . . . . . . . 288 407 498 575 642

500,000 . . . . . . . . . . . . . 182 257 314 362 404

1,000,000 . . . . . . . . . . . . 128 181 221 255 284

2,000,000 . . . . . . . . . . . . 91 127 155 178 198

5,000,000 . . . . . . . . . . . . 57 79 95 108 119

10,000,000 . . . . . . . . . . . 40 54 64 71 76

20,000,000 . . . . . . . . . . . 27 36 40 41 41

Table VI. Estimated standard errors of the ratio of total births

expected per 1,000 black women: National Survey of Family

Growth, 1988

Base of ratio

Estimated ratio

1,000 2,000 3,000 4,000 5,000

500,000 . . . . . . . . . . . . . 120 169 206 237 264

1,000,000 . . . . . . . . . . . . 85 119 144 165 183

2,000,000 . . . . . . . . . . . . 59 82 99 112 123

5,000,000 . . . . . . . . . . . . 37 49 57 62 65

9,000,000 . . . . . . . . . . . . 26 34 37 36 32

Table VII. Estimates of standard errors of percents of total or

total nonblack women: National Survey of Family Growth, 1982

Base of percent

Estimated percent

2 or

98

5 or

95

10 or

90

20 or

80

30 or

70

40 or

60 50

Standard error in percentage points

100,000 . . . . . . . . . . . . . . . 6.5 10.1 13.8 18.5 21.2 22.6 23.1

500,000 . . . . . . . . . . . . . . . 2.9 4.5 6.2 8.3 9.5 10.1 10.3

1,000,000 . . . . . . . . . . . . . . 2.0 3.2 4.4 5.8 6.7 7.2 7.3

5,000,000 . . . . . . . . . . . . . . 0.9 1.4 2.0 2.6 3.0 3.2 3.3

10,000,000 . . . . . . . . . . . . . 0.6 1.0 1.4 1.8 2.1 2.3 2.3

30,000,000 . . . . . . . . . . . . . 0.4 0.6 0.8 1.1 1.2 1.3 1.3

50,000,000 . . . . . . . . . . . . . 0.3 0.4 0.6 0.8 0.9 1.0 1.0

Table VIII. Estimated standard errors of the ratio of total births

expected per 1,000 women: National Survey of Family Growth,

1982

Base of ratio

Estimated ratio

1,000 2,000 3,000 4,000 5,000

200,000 . . . . . . . . . . . . . 381 539 660 761 851

500,000 . . . . . . . . . . . . . 241 340 417 481 537

1,000,000 . . . . . . . . . . . . 170 240 294 339 378

2,000,000 . . . . . . . . . . . . 120 169 207 238 265

5,000,000 . . . . . . . . . . . . 76 106 129 147 163

10,000,000 . . . . . . . . . . . 53 74 88 100 110

20,000,000 . . . . . . . . . . . 37 50 59 65 69

Table IX. Estimated standard errors of the ratio of total births

expected per 1,000 black women: National Survey of Family

Growth, 1982

Base of ratio

Estimated ratio

1,000 2,000 3,000 4,000 5,000

500,000 . . . . . . . . . . . . . 140 197 240 275 306

1,000,000 . . . . . . . . . . . . 98 138 167 190 210

2,000,000 . . . . . . . . . . . . 69 95 114 128 139

5,000,000 . . . . . . . . . . . . 42 56 63 67 67

9,000,000 . . . . . . . . . . . . 30 37 37 31 11

32
test this racial difference at the 0.05 level of significance,

compute

t = =

22.1 – 16.4

[ (22.1)2 RSE2

(22.1) + (16.4)2 RSE2(16.4)]

RSE’s are computed using the appropriate values for B from

table I:

RSE(22.1) = Î5,181 z (100–22.1)

(22.1) z 7,679,000

= 0.049

and

RSE(16.4) = Î10,738 z (100–16.4)

(16.4) z 47,076,000

= 0.034.

Thus

t = =

22.1–16.4

(22.1)2 z (0.049)2 + (16.4)2 z (0.034)2

= 4.68

The two-tailed critical value for a normal statistic and a

significance level of 0.05 is 1.96. Therefore, the difference is

significant at the 5-percent level.

Nonsampling error

Although sampling error affects the reliability (that is,

precision, repeatability) of survey estimates, nonsampling

error may introduce bias (that is, inaccuracy). The results of

any survey are subject to at least four types of nonsampling

error, including interview nonresponse; nonresponse to individual questions or items within the interview; inconsistency

of responses to questions; and error of recording, coding, and

keying by survey personnel.

To minimize nonsampling error, stringent quality control

procedures were introduced at every stage of the survey,

including a check on completeness of the household listing;

extensive training and practice of interviewers; editing of

questionnaires by the interviewers’ supervisors; short verification interviews with a subsample of respondents; verification

of coding and editing; independent coding of a sample of

questionnaires by NCHS; keypunch verification; and an extensive computer ‘‘cleaning’’ to check for inconsistent responses,

missing data, and invalid codes. A detailed description of some

of these procedures follows; others were discussed previously.

Interview nonresponse

Interview nonresponse means that no part of an interview

was obtained. This is conventionally measured by response

rates. Nonresponse to the NHIS was 4 percent, for a response

rate of 96 percent. Among this 96 percent, 82.5 percent of

eligible women responded to the NSFG, for a compound

response rate of 79 percent. Nonresponse did vary by certain

characteristics of the woman but the wealth of information in

the NHIS allowed adjustments to be made for nonresponse.

This nonresponse and the procedures used to adjust for it are

described in detail in references 21 and 22.

Item nonresponse

Item nonresponse may have occurred when a respondent

refused to answer a question, when she did not know the

answer to a question, when the question was erroneously

skipped or the answer was not recorded by the interviewer, or

when the answer could not be coded. The rate of nonresponse

to individual questions was very low in Cycle IV, as it was in

Cycle III. Some examples of item nonresponse from among a

total of 8,450 respondents are as follows: religion, 25 cases

and occupation, 17 cases. The items with the most nonresponse were family income (from which poverty-level income

was derived), with 893 cases, and age (date) of first intercourse, with 458 missing cases.

In the 1988 NSFG, 201 items were forced to be complete;

missing data for these variables were imputed. Of these 201

items, 173 imputed items with imputation flags exist on the

public-use tape. For 116 of these 173, less than 1 percent of

the cases required imputation; for 39, 1–5 percent; for 13,

5–10 percent; and for only 5, 10–11 percent. For those few

items for which the proportion of cases imputed was high, this

fact is noted in the appropriate section of the definitions. This

report only used NSFG variables with imputed missing data.

As with all survey data, responses to the NSFG were

subject to deliberate misreporting by the respondent. Such

misreporting cannot be detected directly, but it can be detected

indirectly by the extensive computer ‘‘cleaning’’ and editing

procedures used in the NSFG.

Table X. Estimated standard errors of the ratio of total births

expected per 1,000 women: National Survey of Family Growth,

1973

Base of ratio

Estimated ratio

1,000 2,000 3,000 4,000 5,000

20,000 . . . . . . . . . . . . . . 232 531 826 1,121 1,416

50,000 . . . . . . . . . . . . . . 147 336 523 709 896

100,000 . . . . . . . . . . . . . 104 238 370 502 634

200,000 . . . . . . . . . . . . . 74 168 262 355 448

500,000 . . . . . . . . . . . . . 47 107 166 225 284

1,000,000 . . . . . . . . . . . . 33 76 118 160 202

2,000,000 . . . . . . . . . . . . 24 54 84 114 144

5,000,000 . . . . . . . . . . . . 16 35 54 74 93

10,000,000 . . . . . . . . . . . 12 26 40 54 68

20,000,000 . . . . . . . . . . . 9 20 30 41 51

33
Appendix II

Definition of terms

Additional births expected—The number of children a

woman expects to give birth to in the future, including a

current pregnancy if applicable. Women who were sterile or

married to sterile men were classified as expecting zero

additional births. Those physically able to have births were

asked whether they, and their current husband or partner if

applicable, intended to have any babies in the future, and, if

so, how many. Women who did not know whether they

intended any future births, or who did not know a particular

number they intended to have, were asked for the smallest and

largest numbers they expected to have. The estimate of

additional births expected in those cases is an average of the

smallest and largest numbers given.

Age—In Cycle IV, age is classified by the age of the

respondent in completed years as of March 15, 1988, the

approximate midpoint of interviewing. In Cycles I and III, age

is classified by the age of the respondent as of the date of the

interview.

Cohort—A group of persons who experience the same

significant event in a particular time period. For example, a

birth cohort may be those born in 1942 or in 1940–44; a

marriage cohort would be those married in a given year or

group of years.

Cohort fertility—Refers to the birth rates of a birth cohort

of women, that is, a group of women who all were born in a

particular time period, for example, in 1942 or 1940–44. The

term ‘‘cohort fertility’’ may be used to refer to completed

cohort fertility.

Completed cohort fertility—Refers to the average total

number of children born to a birth cohort of women when their

childbearing is completed, for example, at ages 47 or older.

Fertility—The childbearing performance of individuals,

couples, groups, or populations—that is, the number of births

they have.

Marital status—In the NSFG, persons were classified by

marital status as married, widowed, divorced, separated, or

never married. Ever married refers to women who are married,

or have been married at some time in their lives—that is,

women whose marital status is currently married, separated,

divorced, or widowed. In Cycle I, which was mainly a survey

of ever-married women, those who reported themselves as

married or as informally married, such as living with a partner

or common law spouse, were classified as currently married. It

is possible that some of these were never formally married, but

nonetheless are considered ‘‘ever married’’ for purposes of this

report. In Cycle I, the informally married comprised only

1.5 percent of total respondents, and 2 percent of currently

married respondents. In Cycles III and IV, surveys of women

of all marital statuses, those who reported themselves as ‘‘not

married, but living with a partner or boyfriend’’ were classified

according to their legal marital status, that is, widowed,

divorced, separated, or never married. In all cycles, women

who were married but separated from their spouses were

classified as separated if the reason for the separation was

marital discord; otherwise, they were classified as currently

married.

Lifetime births expected—See total births expected.

Parity—This refers to the number of live births the

woman has had. For example, a woman classified as ‘‘parity

0’’ has never had a live birth. ‘‘Parity 1 or more’’ means that

she has had one or more live births. Children ever born is also

known as ‘‘parity.’’

Race—Race refers to the race of the woman interviewed

and is reported as black, white, or other. In the 1988 and 1982

NSFG, race was classified according to the woman’s own

report of the race that best described her. In 1973, race was

based on interviewer observation.

Synthetic cohort—A hypothetical cohort of persons that is

represented when data for a year or other brief period are

treated as though they relate to a single cohort. For example,

the total fertility rate, which summarizes the age-specific birth

rates for a population of women in a given year, may be

assumed to represent the average total children born per

woman for a synthetic cohort of women that passed through

life bearing children at the given rates.

Total births expected—The number of children a woman

expects to have by the time she completes her childbearing.

Total births expected is the sum of the number of children ever

born and the number of additional births expected.

Total fertility rate (TFR)—A measure of fertility that

summarizes the rate of childbearing in a given period of time,

often a year. It is derived by summing the age-specific birth

rates for a population of women in the given period. The TFR

is also a hypothetical measure of completed fertility for a

synthetic cohort of women assumed to pass through life

bearing children according to the age-specific birth rates in the

given period. Thus, the TFR may be interpreted as the average

number of lifetime births women may be expected to have if

they bore children at the rates that women of all ages did in the

given year or other period.

34
Appendix III

Items on the 1988 National

Survey of Family Growth

questionnaire related to

birth expectations

35
36