In “No Honey, No Baby: The Relational and Economic Factors Associated With Having Children in America,” Wendy Wang, the institute’s director of research, looks for an explanation of a trend that now seems to buck some of the usual suspects: demographics, economics and family-friendly policy. Her research suggests a lot of separate factors are mingling to lead many young American adults to say “I don’t” to marriage and raising families.

“The decline of marriage goes hand in hand with falling fertility rates, simply because married women have a much higher fertility rate than unmarried women,” Wang writes, noting research by demographer Lyman Stone that shows about half the decline in fertility since 2008 tracks with a much lower marriage rate.

In 2020, the birthrate was 81 per 1,000 married women ages 14-55, and 39 per 1,000 for unmarried women in that age group.