I went and looked up the citation in the post. It's interesting: https://www.nber.org/system/files/working_papers/w23408/w23408.pdf https://www.nber.org/syste

I went and looked up the citation in the post. It's interesting: https://www.nber.org/system/files/working_papers/w23408/w23408.pdf https://www.nber.org/system/files/working_papers/w23408/w234... The thesis of the paper is that fracking increases the incomes of less-educated men, which increases both the marital and non-marital birth rate, but not the marriage rate. They also contrasted with the Appalachian coal boom of the 70s and 80s, which increased marital birth rate and marriage rate but not non-marital birth rate. There's a wide body of research behind that paper linking economic conditions with birth rates, including studies in rodents about early-pregnancy abortions (in most mammals, the mother's body will spontaneously abort a fetus if food & survival conditions are poor); research into sex ratios (more boys than girls are born in times of plenty, while the reverse is true in times of starvation, consistent with males' greater variance of reproductive success); the "hem line hypothesis" (women wear more revealing clothing in boom times, and then more modest clothing in depression); and falling frequency of sex across all age groups and marital statuses in poor economic times. My takeaway is that humans and other mammals are biologically programmed to want to reproduce more when times are good but lose interest and focus on survival when times are bad, but the particular expression of this is culturally mediated and depends a lot on local social mores.