What Are the Prospects for Continued Low Fertility in Japan?

Abstract

The low-fertility trap hypothesis (Lutz, Skirbekk, Testa, Vienna Yearb Popul Res 4:167–192) describes plausible self-reinforcing mechanisms that, if unchecked, would result in a continued decrease of the number of births in countries affected. It postulates that (a) low birth rates lead to fewer women of reproductive age; (b) fertility preferences shaped early in life lead to lower fertility preferences and lower realized fertility in adulthood for generations who have grown up with few siblings; and (c) growing material aspirations lead many couples to postpone childbearing, especially when the relative income of the young decreases. This chapter investigates whether Japan is in a low-fertility trap and finds clear evidence of the first mechanism (rapidly shrinking cohorts of reproductive age), some evidence of the second (value changes resulting in further fertility decline), and some support for the third mechanism (declining relative income among young adults, implying postponed and depressed fertility). Provided that aspirations of young adults grow while the expected income for younger cohorts decreases, partly as a consequence of population aging induced by low fertility, Japan’s fertility could further decline as all three factors would then work toward creating a downward spiral in births. If such mechanisms are indeed at work, this should prompt governments to take action to avoid the trap while that is still possible.