Determinants of Korean Birth Intervals: The Confrontation of Theory and Data

In this analysis, data from the Korean National Fertility Survey of 1974 are used to seek to explain differences in the pace of fertility in terms of differences in contraception, breastfeeding and other intermediate variables. Strong effects are found for these variables, particularly contraception. Nonetheless, virtually none of the effects of the socio-economic variables can be explained in our full model. Overall, our first models, which included only the socio-economic variables, contained 44 significant coefficients. With the introduction of the intermediate variables, only eleven of these coefficients became non-significant (while six others became significant). Thus, though using excellent data, we cannot begin to reproduce what theory predicts. The analysis suggests that this is a consequence of both measurement error and omitted intermediate variables, such as coital frequency. There are strong theoretical reasons for attempting to elucidate the mediating role of proximate variables by using individual data. Nonetheless, these findings, together with similar results obtained by others, strongly suggest that this is not likely to be a fruitful line of future endeavour.