and **speed** of the decline related to socioeconomic development and population policy: Pat and current fertility trends are evaluated and placed within the social, economic and political context of the country. Trmds and anticipated changes in the socio-economic structure and cultur values of the society as well as policies and programmes directed towards family planning are considered vis-a-vis expected trends in fertility (U.N. 1986).

A sc,,&rate approach is applied to some Latin American countries, for which projections<sup>done by the</sup> Centro Latinoamericano de Demograffa (CELADE) are adopted.

For below-replacement countries, the U.N. considers "idiosyncratic characteristics of socioculturd changes' (U.N. 1989), making projections on a case-by-cas basis. 'Heavy emphasis' is actually placed on projections from national statistical offices, though some of these are modified in the ,Wterest of international comparability. These countries are assumed to follow some path back to replacermentlevel fertility, the level that produces an NRR of one when combined with the lowest mortalit) twsumed possible in the projection period.

Besides the medium variant, or most likely scenario, developed according to these principles, high and low variants are also developed. The high variant assumes stabilization with TFR at about<sup>2.5-</sup> 2.6, and the low variant assumes stabilization with TFR at 1.5-1.6 (except for countries<sup>in Latin Amnerica,</sup> for which the CELADE projections are adopted). These variants are meant to provide<sup>a range of</sup> projectioes but not statistical confidence intervals like those proposed by Cohen (1986). In<sup>many cases,</sup> the high ; low variants for the current period are estimates made by national statistical offices; occasionaly, they are estimates made by the World Bank or the U.S. Bureau of the Census.

Fertility levels are expressed in terms of the total fertility rate or the gross reproduction rate, and other fertility measures are derived from it. Fertility levels for projection periods between the<sup>current</sup> and the stable fertility period appear to be derived from models; however, these are not discussed.

U.S. Bureau of **the** Census international projections. The Center for International Research at the Bureau applies separate procedures for low fertility zountries, with TFRs of 2.2 or lower, and high fertility countries. Low fertility countries ar- assumed to have TFRs in 2000 between 1.5 and 1.8 (depending on how low TFR is currently) and in 2050 of exactly 1.7. For intermediate periods, TFRs are obtained by linear interpolation. Age-specific fertility patterns are taken from the latest<sup>empirical</sup> esimates and adjusted proportionally as TFR changes.

These projected TFRs are considerably below World Bank and U.N. medium fertility projections. Applied in combination with World Bank assumptions for mortality and migration,<sup>the</sup> Bureau of the Census procedures would result in some low fertility countries having substantially smaller populations in 2050 than they have currently. Another unit of the bureau makes national projections for the U.S., to be described below. These projections assume that TFR stabilizes early in the next century around 1.9 (with the low and high variants being 1.6 and 2.3).

High fertility countries are assumed to follow a logistic path to lower fertility. Logistic functions are estimated country by country from past data, assuming an upper asymptote equal to one point above the highest recorded TFR in the data (but no lower that 6.0) and a lower asymptote<sup>of 2.0. The</sup> resulting estimats for the year 2000 from applying these functions are required to 'make sense' in relation to 'levels of modern contraception, education among women in the childbearing<sup>ages, and urbanization</sup> **trends"** (U, S. Bureau of the Census 1990). For each country where they do not, an alternative logistic fun.ction is estimated using an assumed TFR for the year 2000, sometimes based on experience of similar countries. Furt} er adjustments may subsequently be made to ensure consistency within regions.

Nadonal projections. Some representative approaches used by national statistical offices or 3