This analysis exploits the variation across states in the timing of policy implementation to determine if family cap policies lead to a reduction in births to women ages 15 to 34. Vital statistics birth data for the years 1989 to 1998 offer no such evidence. The data reject a decline in births of more than one percent. The finding is robust to multiple specification checks. The data also reject large declines in higher-order births among demographic groups with high welfare participation rates.
It's paywall blocked, so I can't see anything but the very beginning of the paper. I can't evaluate its findings.
As a counterpoint, last December, a study out of the U.K. determined that smarter people (defined as those with higher levels of educational attainment or higher fluid intelligence test scores [IQ tests partly measure fluid intelligence]) were less likely to breed.
MODERN life is so cushy that some wonder if human evolution has stopped. Unlikely, reply biologists, for family sizes (and therefore numbers of descendants) still vary. A study just published in the Proceedings of the National Academy of Sciences uses a new statistical method to examine how genetic contributions to certain human traits correlate with how many children a person has. The data came from the UK Biobank, which contains genetic and medical data from half a million people. Positive values mean an association with successful reproduction; negative ones the opposite. Intriguingly, this analysis suggests genetic contributions to intelligence and educational achievement are currently disfavoured by natural selection.