# **Xii** INTRODUCTION

Table 1 Assumed Annual Iccrements to Life Expectancy (in years) in Table 2. A set of medium decrements is also provided, representing "h typical schedule :f improvements toward which rates **_'f_** change converge when the preceding equation is applied successively.

|**Initial**||**Males**|||**Females**||
|---|---|---|---|---|---|---|
|life|||||||
|expec-|||||||
|tany|**Ninim**|**un**<br>Mediun M|aximu|n Mininun|**Medium**M|axinun|
|40|0.22|**0.45**|0.69|0.23|0.48|**0.73**|
|45|0.23|0.48|0.73|<br>0.26|0.53|0.80|
|50|0.24|0.48|0.73|<br>0.27|0.55|0.83|
|55|0.22|0.45|0.69|<br>0.26|0.54|0.81|
|60|0.19|0.39|0.59|<br>0.24|O.S0|0.76|
|65|0.15|<br>0.30|0.45|<br>0.21|0.44|0.66,|
|70|0.09|0.18|0.27|<br>0.17|0.35|Q.52|
|75|0.01|0.03|0.04|<br>0.11|0.23|0.34|
|80||||0.04|0.08|0.12|

c.tection of life tables. tany **Ninimun** Mediun Maximun Mininun **Medium** Maxinun Those life tables are selected from the Coale-Demeny models (Coale and Dcmcny 1983) that provide the projected 40 0.22 **0.45** 0.69 0.23 0.48 life expectancy and infant mortality rates 45 0.23 0.48 0.73 0.26 0.53 0.80 for the first three quinquennia. First, a 50 0.24 0.48 0.73 0.27 0.55 0.83 level of the life tables is chosen to give 55 0.22 0.45 0.69 0.26 0.54 0.81 the desired infant mortality rate 60 0.19 0.39 0.59 0.24 O.S0 0.76 (interpolaticn is used if necessary). 65 0.15 0.30 0.45 0.21 0.44 Mortality rates up to age 14 are taken 70 0.09 0.18 0.27 0.17 0.35 from this life table. Second, another 75 0.01 0.03 0.04 0.11 0.23 0.34 level of the life table is chosen to give 80 0.04 0.08 0.12 rates for ages 15 and older such that the *-^ .'ed level of life expectancy is ootained. Among the four Coale-- not appticabte. Demeny families (North, South, East, and West), that family is chosen which minimizes the divergence between the two chosen levels.

For subsequent quinquennia, only life expectancy is used in determining levels, and the West family is used consistently.

Survivorship ratios from these model life tables were specified for the firsi. three quinquennia and for 2025-30, 2050-55, and 2100-S5. The projection program used, ProjPC-'II (Hill n.d.), was allowed to interpolate linearly for intervening periods, to facilitate a smooth transition across life table families where this was necessary.

Comparison with other mortality projections. These procedures may be compared with the previous procedures with regard to their rationale and to their, effects on projected mortality and population. The change in procedures does produce generally minor, expected differences in results. These procedures were developed from analysis of trends in life expectancy and infant mortality in available national data (Bulatao and Bos 1989). Logistic functions arc used because these fit past trends best, country by country. The schedules of medium change in life expectancy and infant mortality reflect median trends across countries, and the schedules for minimum and maximum change reflect the 10th and 90th percentile when country trends are ranked firc'.,.' -- est to fastest. The equations to predict short-term trends in life expectancy and infant mc a- e were estimated using these data; other socioeconomic factors, like per capita income, dil rr.:. prediction.

The procedures used for projecting mortality in the previous edition were based on earlier data and involved two separate schedules of increments to life expectancy, for countries with high and with low female primary enrolment. Infant mortality was not projected separately, and life tables were chosen based on life expectancies alone.