Wednesday, November 04, 2015

On a relationship between climate change in the United States and falling birth rates

On my RSS feed, I recently came across a paper looking at the relationship between climate change and (American) demographics. NBER Working Paper No. 21681, "Maybe Next Month? Temperature Shocks, Climate Change, and Dynamic Adjustments in Birth Rates", written by Alan Barreca, Olivier Deschenes, and Melanie Guldi, makes some noteworthy claims. The paper is behind a paywall, but the abstract is at least indicative.

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.

My source, the Bloomberg article "Climate Change Kills the Mood: Economists Warn of Less Sex on a Warmer Planet" written by Eric Roston, goes into somewhat more detail about the claims made.

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 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.

If this is correct, it's tempting to wonder about the extent this would be replicated in other areas of the world. What about other warming areas? Does cooling have a relationship to fertility?

1 comment:

Ba-ldei Aga said...

I have a pdf copy