Claim: Warmer Weather Reduces Birth Rates

Guest essay by Eric Worrall

A new study published by the US National Bureau of Economic Research claims that every day over 80F per year dramatically reduces your chances of getting lucky.

According to the NBER;

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

Alan Barreca, Olivier Deschenes, Melanie Guldi

NBER Working Paper No. 21681

Issued in October 2015

Dynamic adjustments could be a useful strategy for mitigating the costs of acute environmental shocks when timing is not a strictly binding constraint. To investigate whether such adjustments could apply to fertility, we estimate the effects of temperature shocks on birth rates in the United States between 1931 and 2010. Our innovative approach allows for presumably random variation in the distribution of daily temperatures to affect birth rates up to 24 months into the future. We find that additional days above 80 °F cause a large decline in birth rates approximately 8 to 10 months later. The initial decline is followed by a partial rebound in births over the next few months implying that populations can mitigate the fertility cost of temperature shocks by shifting conception month. This dynamic adjustment helps explain the observed decline in birth rates during the spring and subsequent increase during the summer. The lack of a full rebound suggests that increased temperatures due to climate change may reduce population growth rates in the coming century. As an added cost, climate change will shift even more births to the summer months when third trimester exposure to dangerously high temperatures increases. Based on our analysis of historical changes in the temperature-fertility relationship, we conclude air conditioning could be used to substantially offset the fertility costs of climate change.

Read more: http://www.nber.org/papers/w21681

The press release in Reuters;

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).

Read more: http://www.bloomberg.com/news/articles/2015-11-02/climate-change-kills-the-mood-economists-warn-of-less-sex-on-a-warmer-planet

The main paper is paywalled, but it seems bizarre to conclude that high temperatures reduce libido and birth rates, given that the highest birth rates in the world are mostly found in tropical countries. I can believe that an abrupt transition from cold to warm weather has an impact, warm weather can knock you about until you acclimatise – but to try to infer an absolute temperature scale from seasonal variations seems a bit of a stretch.