Ultra-low fertility in Korea: the role of tempo effect

Sam Hyun Yoo, Wittgenstein Centre (IIASA, VID/ÖAW, WU) and International Institute for Applied Systems Analysis (IIASA)
Tomas Sobotka, Vienna Institute of Demography

Delayed childbearing is one of the main causes of ultra-low fertility in East Asia, but little is known about the extent of which the ongoing “postponement transition” depresses period total fertility rates in this region. We provide an in-depth analysis of the role of tempo effect in fertility decline in the Republic of Korea, a country that currently experiences very low period total fertility rate (TFR) and, at the same time, has seen a rapid increase in the mean age at first birth to one of the highest levels globally. Using tempo- and parity-adjusted total fertility rate (TFRp*) suggested by Bongaarts and Sobotka (2012), we show that the conventional TFR in Korea has been negatively affected by tempo effect since the early 1980s and tempo effect was the main force pushing the TFR to the “ultra-low” levels below 1.3 since the early 2000s. We also show that the fluctuations in Korean TFR have been strongly driven by changes in the timing of childbearing, with intensive postponement of childbearing largely fueling a rapid TFR decline in the early 2000s to a low of 1.1 in 2005. When tempo and parity composition effects are accounted for, Korean fertility shows more gradual, but continuous decline, falling for the first time to a 1.5 threshold in 2013. The decline in Korean fertility followed distinct phases, with a fall in third and higher-order fertility rates until the 1980s followed by a gradual decline in second-order TFRp* in the 1990s and then a gradual decline in first-birth rates combined with a faster decline in second-order TFRp* since the early 2000s. Further continuation of these trends would imply that Korean fertility would recover only slightly and would stay very low even once the postponement of childbearing comes to an end.