The long-term effect of the timing of fertility decline on population size

Existing long-range population projections imply that the timing of the fer tility transition has a relatively unimportant effect on long-term populati on size when compared with the impact of the level at which fertility is as sumed eventually to stabilize. However, this note shows that the effect of the timing of fertility decline is a function of the eventual fertility rat e: the lower the eventual fertility rate, the greater the effect of the tim ing of the transition becomes. This finding has important implications for projection methodology, as well as for policies related to the consequences of long-term levels of population size.