Xli INTRODUCTION in Table 2. A set of medium decrements is also previded, representing the typical sQcdcu'ie af improvements toward which rates oi change converg_s when. the preceding equation is applied suc 'ssively.

Table 1 Assumed Annual Increments to Life Expectancy (in years)

|when. the preceding equation is applied<br>suc'ssively.|Initial<br>tifo||males|||Femal|es|
|---|---|---|---|---|---|---|---|
||expec-|||||||
|Selectionof life tables.|tancy|Minimun|NedlunM|aximu|nminimu|nMediun|Maxinun|
|Those life tables are selkt:d from the||||||||
|oale-Demeny models (Coale and||||||||
|<br>Demeny 1983) that provide the projected|40|0.22|0.45|0.69|0.23|0.48|0.73|
|lifc expectancy and infant mortality rates|45|0.23|0.48|0.7S|0.26|0.53|0.80|
|fo. the first three quinquennia.<br>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<br>desired<br>infant<br>mortality<br>rate|60|0.19|0.39|0.59|0.24|0.50|0.76|
|(interpolation<br>is used<br>if necessary).|65|0.15|0.30|0.45|0.21|0.44|0.66|
|Mortality<br>rates up to age 14 are taken|70|0.09|0.18|0.27|0.17|0.35|0.52|
|from this life table.<br>Second, another|75|0.01|0.03|0.04|0.11|0.23|0.34|
|level of the life table is chosen to give|s o-||||0.04|0.08|0.12|
|rates fot' ages 15 and older such that the||||||||
|desired level of life expectancy is||||||||
|obtained.<br>Amrnbthe four Coale-|--not|appticable|.|||||
|Demeny families (North, South, East,||||||||
|and West), that family is chosen which m|inimizes t|he diverg|ence be|tween|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 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). Lo.istic functions are 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 from sloweat 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 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 tablv' were chosen based on life expectancies alone.