The effects of childbearing on married women's labor supply and earnings - Using twin births as a natural experiment

We use exogenous variations in fertility due to twin births to measure the impact of an unplanned child on married women's labor supply and earnings. Although the overall effects of an unplanned birth on labor supply are small, we find significant effects in the years immediately following the unplanned birth, especially in 1970. We estimate that declining fertility explains between 6 and 13 percent of the increase in married women's labor supply between 1970 and 1980. Twin births are also associated with a substantial short-run loss in earnings. This effect persists longer than the labor supply effects, though it does eventually disappear.