I imagine there's a bimodal distribution at work here: wealthier couples could choose to get married in a traditional ceremony (which is often an economic flex

I imagine there's a bimodal distribution at work here: wealthier couples could choose to get married in a traditional ceremony (which is often an economic flex as much as anything else), although in such circles prenup agreements related to divorce-related division of wealth seem increasingly common. If you're going to have a prenup, why get married at all? There are issues related to end-of-life-decisions but the living will solves that problem. This is where 'changing social values' apply, in that non-married living arrangments don't lead to social ostracization as they might have in the past. The other side is simply economic - getting married and raising a family is an expensive proposition that many people (at least in the United States) can no longer afford, and there's no real social safety net that ensures medical care and quality education for low-income families - so raising a family in poverty is not an attractive proposition. There's also good evidence that birth rates track economic recessions pretty closely: https://www.pewresearch.org/social-trends/2010/04/06/us-birth-rate-decline-linked-to-recession/ https://www.pewresearch.org/social-trends/2010/04/06/us-birt... This economic factor seems universal, as the high cost of housing in China is associated with a decreased marriage rate (although unequal numbers of men and women related to the now-defunct One Child policy is another issue): https://www.nature.com/articles/s41599-022-01400-4 https://www.nature.com/articles/s41599-022-01400-4