Maybe Next Month? Temperature Shocks and Dynamic Adjustments in Birth Rates

Abstract

We estimate the effects of temperature shocks on birth rates in the United States between 1931 and 2010. We find that days with a mean temperature above 80°F cause a large decline in birth rates 8 to 10 months later. Unlike prior studies, we demonstrate that the initial decline is followed by a partial rebound in births over the next few months, implying that populations mitigate some of the fertility cost by shifting conception month. This shift helps explain the observed peak in late-summer births in the United States. We also present new evidence that hot weather most likely harms fertility via reproductive health as opposed to sexual activity. Historical evidence suggests that air conditioning could be used to substantially offset the fertility costs of high temperatures.

Ambient temperature, birth rate, and birth outcomes: evidence from South Korea

“…5 Studies on the effect of temperature on birth outcomes have shown mixed results. Some studies found that high temperatures cause a low birth weight (Deschênes et al 2009;Andalón et al 2016;Barreca et al 2018) and preterm births (Dadvand et al 2011;Strand et al 2011;Barreca et al 2018), possibly because, at high temperatures, blood flow to the uterus decreases (Basu et al 2010) and the body secretes stress hormones, such as cortisol (Yackerson et al 2008). However, other studies found no significant effect on birth outcomes (Porter et al 1999;Tustin et al 2004;Lee et al 2008).…”

“…These variables are included because the mother's characteristics are likely to affect the number of births. Although the maximum temperature in a city on a given day is determined randomly, following Barreca et al (2018), this study includes a variety of fixed effects in the regression to address the confounding of unobserved factors. In the equation, η is the city/month fixed effect, and thus the birth rate of the same city/month is compared over time.…”

“…Few studies have analyzed the relationship between temperature and birth rate. Those that have include Seiver (1985Seiver ( , 1989, Roenneberg and Aschoff (1990), Miron (1991, 1996), and Barreca et al (2018). They used relatively old data, 1 and found a negative relationship between temperature and birth rate; that is, high temperatures reduce the number of births.…”

“…They used relatively old data, 1 and found a negative relationship between temperature and birth rate; that is, high temperatures reduce the number of births. Barreca et al (2018), the most recent of the studies, examined data obtained between 1931 and 2010 and found that an additional day with a mean temperature of 80°F or higher decreased birth rates 8, 9, and 10 months later, but increased them 11-23 months later; the net effect of these findings is equal to a decrease in birth rate of 0.33%. The study also found that an additional day with a temperature of 80°F or higher increased the current month's birth rate and decreased that of the following month.…”

The demand for season of birth

“…Recent work by Barreca, Deschenes, and Guldi () documents that short‐term shifts in conception weeks in response to very hot days result in birth rate declines 8–10 months later and increases in summer births. However, their paper does not consider preferences for season of birth or how maternal characteristics are related to birth seasonality or spring in particular.…”