age-specific mortality rates. For many countries with complete vital registration, quinquennial life expectancy at birth Egures are estimated from Coale-Demeny model life tables, selected on the bas,s of IMR, CDR, and tiie age disti-ibution. Current or very recent single-year life expectancies for all but a few countries are interpolated between the estimated 1985-89 average life expectancy and the 1990-94 projected life expectancy (See below on how mortality indicators are projected).

For countries without complete vital registration, single-year estimates are interpolations between projetted quinquennial figures. The usual procedure for constructing a current IMR estimate is to use an estimate from any previous time that has been derived from a census or survey, eithler from retrospectively collected birth histories, or more commonly, through indirect estimation techniques such as the Brass methods (United Nations 1990). Life expectancy at birth estimates are frequently derived from IMR and q5 estimates from surveys or censuses with model life tables. As an example of how these procedures work, consider estimates for Indonesia. The DHS conducted in Indonesia yielded an Indirect estimate of the IMR of 72 (calculated with a Brass procedure) for the period 1982-86. This estimaie was then projected with the Bank IMR projection model to 1985-89 and lo 1990-94. A 1989 IMR estimate was obtained through linear interpolation of the 1985-89 and 1990-94 projections. Life expectancy at birth for 1982-86 was obtained by fitting a Coale-Demeny "North" model Wife table ("North" was selected on the basis of prior analysis of the 1980 census) to the IMR and q5 survey estimates, which were subsequently projected with the Bank life expectancy projection model to 1985-89 and 1990-94. A 1989 life expectancy at birth estimate was obtained through linear interpolation of the 1985-89 and 1990-94 projections. While the availability of the latest empirical data differs, the above approach is similar for many countries.

# _Model lWfe tables_

Mortality estimates for many countries are approximated with model life tables constructed by A. Coale and P. Demeny. Model life tables are used here tc estimate the IMR and life expectancy from indirect estimates (Brass procedures) of child mortality, and to estimate life expectancy from registration derived IMR estimates (often in coniunction with CDR and age structure information). Besides Coale-Demeny, the United Nations (1983) has constructed mode' life tables, which are used in some of the estimates obtained from _World Population Prospects 1990._ The Coale-Demeny model life tables are derived from over 300 empirical life tables and consist of four broad patterns of mortality called "families": North, South, East, and West. Within each of the families, mortality ranges from high to low; a recent extension of the Coale-Demeny tables by Coale and Guo (1991) adds life tables for very low mortality populations. The North family, based on Scandinavian life tables, is characterized by relatively low infant and old age mortality, and high adult mortality. The South family, based on Mediterranean country life tables, has relatively high qs, low adult mortality, and high mortality over 65. The East family, primarily based on Central European country life tables, has relatively high infant and old-age mortality, and relatively low child and adult mortality. The West family is based on 130 life tables from countries all over the world which were considered accurate but did not fit the pattern for the three other families. The West family life tables are selected when no information on the pattern of mortality is available.

# _World Bank projections of mortalty indicators_

As noted above, current estimates of mortality are frequently projections of estimates for previous years or periods, and single-year estimates for current years are often interpolations between 1985-89 and projected 1990-94 figures. When current estimates are from _World Populat;on Prospects_ 4