# l0xx DATA AND METHODS

Table A Assumedannaldecrements Table A2 Assumed annual decrements to infant mortality rate the extended life expectancy assumptions employed.

# _Selection of life tables._

<!-- Start of picture text --> Initial<br>infant<br>mortality<br>rate Mininuun Medf Lsn Maxln.si<br>iSO 0.83 2.08 4.02<br>150 0.8932 2.32 4.47<br>130 1.00 2.50 4.81<br>120 1.13 2.63 5.03<br>110 1.16 2.69 5.15<br>100 1.16 2.71 5.16<br>90 1.14 2.66 5.07<br>80 1.10 2.56 4.86<br>70 1.03 2.41 4.56<br>60 0.93 2.20 4.16<br>50 0.81 1.94 3.65<br>40 0.67 1.62 3.05<br>30 0.50 1.26 2.35<br>20 0.31 0.84 1.56<br>10 0.09 0.36 0.68<br><!-- End of picture text --> Those life tables are selected from the Coale-Demeny models (Coale and Demeny 1983) that provide the projected life expectancy and infant mortality rates for the first three quinquennia. First, a level of the life tables is chosen to give the desired infant mortality rate (interpolation is used if necessary). Mortality rates up to age 14 are taken from this life table. Second, another level of the life table is chosen to give rates for ages 15 and older such that the desired level of life expectancy is obtained. Among the four Coale-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 first three quinquennia and for 2025-30, 2050-55, and 2100-05. The projection program used, ProjPC-II (Hill, forthcoming ), was allowed to interpolate linearly for intervening periods, to facilitate a smooth transition across life table families where this was necessary.

## _Projectingferity_

Future fertility trends are specified by quinquennial total fertility and by a year when the net reproduction rate reaches unity, i.e., when the average woman's fertility results in exactly replacing herself. (This is referred to here as the replacement year.) Separate procedures are applied for three stages of the fertility transition: the pretransition stage, when fertility is high and sustained fertility decline has not started; the transition stage, when fertility is high to medium and sustained fertility decline is in progress; and the late-transition and posttransition stage. We discuss procedures for determining total fertility in each stage and then explain what age-specific patterns of fertility were applied.

For current purposes, a fertility transition is assumed to have started if a country has experienced a drop in total fertility of at least .5 points over any five-year period, or if total fertility is already below 4.5 after a more gradual decline (Bulatao and Elwan 1985). The pretransition stage is the stage before any such decline is evident. The late-transition and posttransition stage is defined by a total fertility rate one point above replacement level (about 3.15) or lower.

Countries in the pretransition stage are assumed to start a fertility transition in the quinquennium after combined male and female life expectancy reaches 50 years, but in no case later than 2005. The life expectancy threshold is slightly lower than the threshold of 53 years previously shown to be a universal precondition, though not a sufficient condition, for the start of fertility transition (Bulatao and Elwan 1985). Until a transition starts, total fertility is assumed to be constant. The one exception is where sterility is a significant factor; sterility is then assumed to decline linearly