This chapter addresses the global evidence of a strong relationship between relative cohort size and fertility, even in developing nations during the fertility transition. “Demographic transition” is the period during which a country passes from high to low death and birth rates. Relative cohort size has played a crucial role in bringing about the fertility transition in developing countries during that period. Total fertility rates are constant or even increasing until relative cohort size begins to increase: at that point, the total fertility rate begins to decline. Relative cohort size can...

This chapter addresses the global evidence of a strong relationship between relative cohort size and fertility, even in developing nations during the fertility transition. “Demographic transition” is the period during which a country passes from high to low death and birth rates. Relative cohort size has played a crucial role in bringing about the fertility transition in developing countries during that period. Total fertility rates are constant or even increasing until relative cohort size begins to increase: at that point, the total fertility rate begins to decline. Relative cohort size can be thought of as the mechanism that prevents excessive rates of population change—reducing fertility when previous high rates, in combination with low mortality rates, have caused relative cohort size to increase, and increasing fertility when previous low rates have caused relatively small younger cohorts.