[영문]The possible negative consequences of current low fertility levels are causing increasing concern, particularly in countries where the total fertility rate is below 1.5. Social inertia and self-reinforcing processes may make it difficult to return to higher levels once fertility has been very low for some time, creating a possible “low-fertility trap.” Policies explicitly addressing the fertility-depressing effect of increases in the mean age at child-bearing (the tempo effect) may be a way to raise period fertility to somewhat higher levels and help escape the “low-fertility trap” before it closes. Reforms in the school system may affect the timing of childbearing by lowering the age at completion of education. A more efficient school system, which provides the same qualifications with a younger school-leaving age, is potentially capable of increasing period fertility and hence exerting a rejuvenating effect on the age composition, even if the levels of cohort fertility remain unchanged. Such policies may also have a positive effect on completed cohort fertility.