Total number of births shrinking faster than fertility rates: fertility quantum decline and shrinking generation size in South Korea

South Korea’s total fertility rate reached 1.3 in 2001 and hit a record low (0.92) in 2019. The total number of births shrank even faster, recording a 45.9 per cent drop between 2001 and 2019. To understand the declining births and the contributing demographic factors, I decompose the change in the birth rate into mean generation size, fertility quantum, and tempo distortions, and evaluate their relative contributions to the decline. The remarkable birth decline since 2001 is largely explained by fertility quantum decline, especially for second births, and shrinking generation size caused by the decline in female population size. Tempo distortions were strong, but given the marginal change since 2001, they contributed less and only in recent years. This study highlights unique features of East Asia’s low fertility, such as continued fertility decline and the long-term negative effects of reproducing generations’ low fertility. Findings might have implications for developing countries experiencing rapid fertility decline.