**<u>Woman’s birth cohort:</u>** The younger the woman, the lower the son preference in both 1991 and 2003.  This confirms the trend found in reported son preference in Table 2, and shows that the trend remains significant even after controlling for many socio-economic, and cultural factors associated with son preference.

**<u>Secular trend 1991-2003:</u>** From the model with the pooled sample of women in the 1991 and 2003 surveys, we found a strikingly large and significant secular trend between 1991 and 2003. Controlling for all the above independent variables, the odds ratio of stating “must have a son” was only 0.34 in 2003 as compared with 1991.

# **6. Why is son preference declining? A decomposition analysis**

We now turn to analyzing the relationship between Korea’s socio-economic development (as measured by education and urbanization), and the decline in reported son preference between 1991 and 2003. To do this, we decompose the respective contributions of (a) changes between 1991 and 2003 in “population composition”, i.e. the proportions of the population who are ⎯ educated or living in urban areas holding each group’s intensity of son preference constant at 1991 levels; and (b) change in “social norms” between 1991 and 2003, i.e. lower level of son ⎯ preference within a given education or urban/rural residence group holding the population composition constant at their 2003 levels.

There have been rapid changes in “population composition”, as well as in “social norms” during this period. Table 1 shows the dramatic increases in levels of education and urbanization in South Korea. Table 5 shows the sharp decline between 1991 and 2003 in the odds ratio of stating “must have a son”: in 2003, it is roughly one-third of its 1991 level within any given category of education and urban/rural residence. The exception to this is in rural areas, where the odds ratio dropped to less than one-fifth its 1991 level. This is especially notable because it implies rapid diffusion of new norms to rural areas, and consequent homogenization between rural and urban areas.

The results of the decomposition are shown in Table 6, and show the contribution of each variable to the overall decline in the probability of stating “must have a son” over the period 1991-2003, _other things equal_ . The most striking result is that change in social norms accounts for as much as 73 percent of this decline, and only 27 percent of the decline is accounted for by changes in population composition (increases in education and urbanization). This is consistent with the findings in Table 2, which shows that son preference declined with birth cohort, and also that women of the same birth cohorts were far less likely to report strong son preference in 2003 compared with 1991. It is also consistent with Table 5, which shows similar declines in son ⎯ preference across all education and urban/rural groups except among rural residents, who actually showed a steeper decline in son preference than urban residents.

That there was widespread change in social norms across the entire population between 1991 and 2003 is indicated by the fact that the estimate of the constant term is significant, positive and very large. The inclusion of the constant term renders the association between son preference and education insignificant, and urban residence becomes associated with increased son preference (see also Table 5). When the constant term is eliminated (results not shown), husband’s education and urban residence become significantly associated with lower son preference. However, the overall results are fairly similar across the two models: changes in social norms account for 73% of the total change with constant term, and 81% without it.

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