An extra “hot day” (the economists use quotation marks with the phrase) leads to a 0.4 percent drop in birth rates nine months later, or 1,165 fewer deliveries across the U.S. A rebound in subsequent months makes up just 32 percent of the gap.
The researchers, who hail from Tulane University, the University of California-Santa Barbara, and the University of Central Florida, believe that their findings give policymakers three major things to think about.
1. Birth rates do not bounce back completely after heat waves.
That’s a problem. As summers heat up, developed countries may see already low birth rates sink even lower. Plunging birth rates can play havoc with an economy. China’s leaders recently acknowledged this by ditching the longtime one-child policy and doubling the number of children couples are allowed to have. A sub-replacement U.S. birthrate means fewer workers to pay Social Security benefits for retirees, among other consequences.
2. More autumn conceptions means more more deliveries in summer.
Infants experience a higher rate of poor health with summer births, “though the reasons for worse health in the summer are not well-established,” the authors write. One possibility may be “third-trimester exposure to high temperatures.”
3. Air conditioning might prove to be an aphrodisiac.
Control over the climate at home might make a difference. The researchers suggest that the rise of air conditioning may have helped offset some heat-related fertility losses in the U.S. since the 1970s.
The paper’s title is about as lascivious as the National Bureau of Economic Research gets: “Maybe Next Month? Temperature Shocks, Climate Change, and Dynamic Adjustments in Birth Rates.” The researchers assume that climate change will proceed according to the most severe scenarios, with no substantial efforts to reduce emissions. The scenario they use projects that from 2070 to 2099, the U.S. may have 64 more days above 80F than in the baseline period from 1990 to 2002, which had 31. The result? The U.S. may see a 2.6 percent decline in its birth rate, or 107,000 fewer deliveries a year.
Just when you thought climate change policy couldn’t get any less sexy (PDF).