Birth Spacing and Sibling Outcomes
利用NLSY79数据，通过工具变量法处理内生性，发现生育间隔每增加一年可使年长子女的考试成绩提高约0.17个标准差，但对年幼子女无显著影响。
Using the NLSY79 and NLSY79 Child and Young Adult Surveys, we investigate the effect of the age difference between siblings (spacing) on educational achievement. Because spacing may be endogenous, we use an instrumental variables strategy that exploits variation in spacing driven by miscarriages. The IV results indicate that a one-year increase in spacing increases test scores for older siblings by about 0.17 standard deviations. These results are larger than the OLS estimates, suggesting that failing to account for the endogeneity of spacing may understate its benefits. For younger siblings, we find no causal impact of spacing on test scores.