Theory and evidence of the effect of modern contraceptives on birth spacing

Jungho Kim, Vienna Institute of Demography

This paper examines the effect of family planning programs on birth spacing both theoretically and empirically. Despite the recent development of dynamic models of fertility, there is no general prediction regarding the effect of modern birth control methods on birth spacing. By considering a simple dynamic model of fertility first introduced by Heckman and Willis (1975), I derive conditions under which an introduction of modern contraceptives leads to women having either longer or shorter birth intervals. The empirical findings in Indonesia suggest that the introduction of modern methods of birth control led to shorter birth intervals in the 1970s and longer birth intervals in the 1990s. Then, I discuss the validity of the conditions of the model in understanding Indonesian experience.