Explaining the sharp decline in birth rates in Canada and the United States in 2020.

Birth rates in Canada and the United States declined sharply in March 2020 and deviated from historical trends. This decline was absent in similarly developed European countries. We argue that the selective decline was driven by incoming individuals, who would have traveled from abroad and given birth in Canada and the United States had there been no travel restrictions during the COVID-19 pandemic. Furthermore, by leveraging data from periods before and during the COVID-19 travel restrictions, we quantified the extent of births by incoming individuals. In an interrupted time series analysis, the expected number of such births in Canada was 970 per month (95% CI, 710-1200), which is 3.2% of all births in the country. The corresponding estimate for the United States was 6700 per month (95% CI, 3400-10 000), which is 2.2% of all births. A secondary difference-in-differences analysis gave similar estimates, at 2.8% and 3.4% for Canada and the United States, respectively. Our study reveals the extent of births by recent international arrivals, which hitherto has been unknown and infeasible to study.