Local Instruments, Global Extrapolation: External Validity of the Labor Supply–Fertility Local Average Treatment Effect
研究了Angrist和Evans用前两胎同性作为工具变量估计生育对劳动供给影响的局部平均处理效应（LATE）在139个国家-年份普查数据中的外部有效性，发现参考样本足够大时外推效果较好，但准确性取决于目标与参考情境的协变量相似度。
We investigate the external validity of local average treatment effects (LATEs), specifically Angrist and Evans's use of same sex of the two first children as an instrumental variable for the effect of fertility on labor supply. We estimate their specification in 139 country-year censuses using Integrated Public Use Microdata Sample-International data. We compare each country-year's actual LATE to the extrapolated LATE from other country-years. We find that, with a sufficiently large reference sample, we extrapolate the treatment effect reasonably well, but the degree of accuracy depends on the extent of covariate similarity between the target and reference settings.