Research

World War II spurred an unprecedented exodus of teachers from American schools, primarily men leaving for military service. Using a difference-in-differences framework that exploits geographic variation in the pre-war gender composition of the teacher workforce and students' ages, I estimate the effects of childhood exposure to this teacher supply shock on educational attainment and labor market outcomes. Increased exposure reduces high school and college completion, as well as adult income. States more affected by this shock responded by hiring more teachers on emergency licenses, resulting in a decrease in teachers' educational attainment. These changes in the composition of the teacher workforce persisted long after the war, suggesting that even temporary shocks to teacher supply can have lasting impacts on student outcomes through changes in teacher quality.

This paper revisits World War II's effect on female labor force participation (FLFP) using newly available complete count census data from 1940 and 1950. I replicate two seminal papers—Acemoglu, Autor, and Lyle (2004) and Goldin and Olivetti (2013)—which use the state-level military mobilization rate of men as a source of variation in women's labor supply. When applying their specifications to the complete count data, I find substantially smaller and typically insignificant effects of the war on FLFP. The mobilization rate is therefore a weak instrument for growth in FLFP, calling into question estimates that use mobilization to instrument for FLFP's effects on wages. I repeat these analyses using 10,000 random 1% subsamples of the complete count data, comparable to the 1% samples used by these authors. In all cases, the distribution of estimates varies widely, suggesting that different census samples can generate very different conclusions when estimating the effects of state-level treatment. These findings challenge previous conclusions about WWII's impact on women's labor force participation and highlight broader methodological concerns for research using small census samples.