A decomposition of declining crude birth rate in South Korea, 1990–2015

While other countries have experienced a gradual decline in CBR since the 1990s, South Korea has shown a rapid decline and now has one of the lowest rates in the world. To identify what drives the decline of CBR, we apply a decomposition developed by Das Gupta (1993) to Korean registry data (KOSIS) and decompose CBR from 1990 to 2015 into four demographic factors: (1) the proportion of women of reproductive age, (2) the age structure of women of reproductive age, (3) the proportion married among women at each age group, and (4) the marital birth rate at each age group. The results show that the proportion of married among women is the main contributor to the decrease in CBR; a decline in the marriage rate is largely responsible for the low birth rate. The proportion of women of reproductive age and age structure of women of reproductive age are other factors lowering the CBR. Meanwhile, the marital birth rate contributes to an increase in CBR. Although some of the increases produced by marital birth rates could be an artifact of timing changes, the impact reflects the patterns of postponing marriage, which leads to more rapid births after marriage. This study uncovers important demographic factors like decreasing proportion married, the shrinking population in reproductive ages, and ageing among Korean women that drive the decline of CBR.