From Local to Global: External Validity in a Fertility Natural Experiment

Abstract

We study issues related to external validity for treatment effects using over 100 replications of the Angrist and Evans natural experiment on the effects of sibling sex composition on fertility and labor supply. The replications are based on census data from around the world going back to 1960. We decompose sources of error in predicting treatment effects in external contexts in terms of macro and micro sources of variation. In our empirical setting, we find that macro covariates dominate over micro covariates for reducing errors in predicting treatments, an issue that past studies of external validity have been unable to evaluate. We develop methods for two applications to evidence-based decision-making, including determining where to locate an experiment and whether policy-makers should commission new experiments or rely on an existing evidence base for making a policy decision.

“From Local to Global: External Validity in a Fertility Natural Experiment” with Cristian Pop-Eleches and Cyrus Samii.

• Journal of Business and Economic Statistics, Volume 39 (Number 1), pp. 217-243.
• Download the paper here
• A non-technical summary of our findings at the LSE’s International Growth Centre’s blog.
• National Bureau of Economic Research Working Paper No. 21,459 (August 2015).
• IZA Discussion Paper No. 9300 (August 2015).
• NYU Wagner Research Paper No. 2647649 (August 2015).
• CESifo Working Paper No. 5493 (August 2015).