Marijuana Legalization and Fertility

State-level marijuana legalization has unintended consequences, including its effect on fertility. Marijuana use is associated with behaviors that increase fertility as well as physical changes that lower fertility. In this paper, I provide the first causal evidence of the effects of recreational marijuana legalization on birth rates using a difference-in-differences design that exploits variation in marijuana legalization across states and over time. The main result is that legalizing recreational marijuana decreases a state’s birth rate by an average of 2.78 percent. Heterogeneity analysis shows that the largest decrease in the birth rate occurs among women close to the end of their childbearing years. I find suggestive evidence of increases in days of marijuana use per month and in the probability of being sexually active. Together, these findings show that the physical effects of marijuana use have the dominant effect on fertility. Finally, I examine the effects of medical marijuana legalization on fertility and find a smaller, statistically insignificant decrease in the birth rate, which is consistent with the smaller increase in marijuana use that results from medical legalization.