# Xii INTRODUCT ON

Table 1 Assumed Annual Increments to Life Expectancy (in years) in Table 2. A set of medihm decrements is also provided, representing the typical schedule of impr. mncnts toward which rates of change converge when the preceding equation is applied successively.

|Initfal<br>||Hates|||Females||
|---|---|---|---|---|---|---|
|life||_|||||
|expec-|||||||
|tancy|Minimun|Nedfu|m Ma4imu|m Mlninui|m Medium M|aximum|
|40|0.22|0.45|<br>0.69|0.23|0.48|0.73|
|45|0.23|0.4b|0.73|<br>0.26|0.53|0.80|
|50|0.24|0.48|<br>0.73|<br>0.27|0.55|0.83|
|55|0.22|0.45|0.69|0.26|0.54|0.81|
|60|0.19|0.39|<br>0.59|0.24|0.50|0.76|
|65|0.15|0.30|<br>0.45|<br>0.21|0.44|0.66|
|70|0.09|0.18|0.27|0.17|0.35|0.52|
|75|0.01|0.03|0.04|0.11|0.23|0.34|
|80|--|--||0.04|0.08|0.12|

Selection of life tables. tancy Minimun Nedfum Ma4imum Mlninuim Medium Maximum Those Ufe tables are selected from tI'Coale-Demeny models (Coale and Demeny1983)thatprovidetheprojected 40 0.22 0.45 0.69 0.23 0.48 0.73 life expectancy and infant mortality rates 45 0.23 0.4b 0.73 0.26 0.53 0.80 for the first three quinquennia. First, 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 0.50 0.76 (interpolation is used if necessary). 65 0.15 0.30 0.45 0.21 0.44 0.66 Mortality rates up to age 14 are taken 70 0.09 0.18 0.27 0.17 0.35 0.52 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 desired level of life expectancy is obtained. Among the four Coale-- not applicable. 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 consistmntly.

Survivorship ratios from these model life tables were specified for the first three quinquennia and for 2025-30, 2050-55, and 2100-05. 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 are used because these fit past trends best, country by country. The schedules of medium change in life expectancy and infanL 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 from slowest to fastest. The equations to predict short-term trends in life expectancy and infant mortality were estimated using these data; other socioeconomic factors, like per capita income, did not improve prediction.

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