I think the best plausible hypothesis to explain the global decline in fertility is something due to phones and the internet: • time displacement, crowds out other social activities • digital mediated culture shifts, increasing divergence between men+men so couple formation is down • other activities are more fun. ie go on trips and share the consumption on social media • amplifies modernity transition and norm shift towards individualism as opposed to family/collective goals • possibly impacts moods, distraction, comparison and contributes to anomie I'm open to other factors — higher housing costs, daycare costs, etc. As well as amplification channels (when others don't have kids, society adapts and having kids is harder). As well as tempo shifts (timing) to a degree. But there are few other plausible mechanisms which could account for the globally synchronized nature of fertility declines. It sort of happens everywhere that gets high-speed internet, social media, and cell phones.

@cojobrien @mattsclancy France interesting here too — was 1.97 as late as 2014, but down to 1.64 in 2023 (latest data suggest 1.56 in 2025).

@benbawan One implication is European societies, particularly N European ones with norms around gender egalitarianism, work life balance, and kids leave the home after 18 seem to be in relatively good shape

@jmhorp What we know in the US is that people under 30 are at unprecedentedly low rates of fertility, which mirrors trends elsewhere. There is a debate the extent to which higher fertility later in the life can counteract; but still a question why it fell in the first place

@anup_malani @lymanstoneky Another response is we need to separate the LDC countries (where I think these dynamics are stronger, but there are pre existing trends) from more developed countries, which were generally increasing or anything pre 2008