# Introduction

This paper discusses the sources of the infant mortality rate (IMR) and life expectancy at birth for each of the 186 countries for which the Population and Human Resources Department at the World Bank makes demographic estimates and projections. Its purpose is to give some background on the derivation of mortality estimates used in the World Bank's demographic estimates and projections to provide users of the data with information on their recency and reliability. The paper attempts to do t'iis through a general discussion of mortality projection methodology and a listing of the sources arnd dssumptions usci lii constructing estimates for individual countries, It is envisioned that a companion paper on the sources of fertility estimates will be issued in the future.

The paper consists of two sections. The first section gives an overview of the sources, discusses their nature, and explains the projection methodology used to obtain current estimates. The second section provides the documentation of mortality sources for each country, organized by region.

## _Frequently used sources_

The single most frequently used source for both the IMR and life expectancy at birth for the 1985-89 base period is _World Population Prospects 1990,_ published by the Department of International Economic and Social Affairs of the United Nations. This publication contains quinquennial estimates and projections made by the U.N. Population Division for 152 countries for the period 1950 to 2025. The Population Division revises its estimates when new data or analyses become available and issues _World Population Prospects_ biennially. In constructing its estimates, the Population Division considers population censuses, demographic and health surv.-.;s, vital registration data, and uses analyses of others as well as its own. Data are adjusted to achieve consistency among vital rates, age structure, and total population. Demographers at the Werld Bank have a working arrangenent to receive further details concerning the original sources consulted, their quality, and the adjustments applied from the demographers in the Estimates and Projections section of the Population Division. _World Population Prospects 1990_ is the first source considered for Bank estimates of mortality, but other sources are used for the 34 countries for which the U.N. does not make estimates, for countries for which more recent data are available from other sources, and when analysis in the Bank indicates different rates.

Another frequently used source is _Population and Vital Statistics Report,_ which is a quarterly publication of the Statistical Office of the U.N. Department of International Economic and Social Affairs. This publication gives the latest official estimates of vital rates from registration data, as well as an indication of the completeness of registration coverage. The reported estimates are sometimes more recent than were consideied by the U.N. Population Division for _World Population Prospects 1990._ Figures appear in _Population and Vital Statistics Report_ even when the registration system is not complete or when rates are internally inconsistent. Bank estimates are taken from this publication only when the U.N. Statistical Office indicates that vital registration is complete (covering at least 90 percent of vital events occurring in a given year). _Population and Vital Statistics Report_ gives registered deaths and registered infant deaths, but not life expectancy figures, which have to be estimated with life tables from the information given for the CDR or IMR or gathered from other sources.

Eurostat, the Statistical Office of the European Community (EC), annually publishes _Demographic Statistics,_ which includes IMR as well as life expectancy estimates from vital registration systems of the EC member countries. These are mostly very recent estimates, and given the near2