Two things I'd say here. First, is that the 'hereditary' nature of religion is even stronger than I assumed. 84% of adults (quite relevant as we skip the rebell

Two things I'd say here. First, is that the 'hereditary' nature of religion is even stronger than I assumed. 84% of adults (quite relevant as we skip the rebellious teen years) who were raised in e.g. a completely Protestant home are Protestants themselves. That bumps up to 89% in households where their parents regularly talked about religion! The relationship is likely even stronger for more 'rigorous' religions such Islam or Haredi Judaism, religions which also correlate extremely strongly with fertility. The second thing is that you're likely dramatically overestimating the secular population. Gallup has been polling people on religion since 1948. Here [1] are those data. As recently as 2004, the percent of people with no religion was in the single digits, so the overall relevance was low. And the inverse correlation between secularity and fertility is also quite new driven by a rather large number of new factors - antagonistic attitude towards gender roles, the embrace of non-marital sex largely enabled by the introduction of the birth control pill in 1960, and so on. So in general, we're entering into relatively uncharted waters, but it's not hard to see what lies ahead as consequences of fertility decisions lag behind those decisions themselves by ~60 years. [1] - https://www.pewresearch.org/religion/2016/10/26/links-between-childhood-religious-upbringing-and-current-religious-identity/ https://www.pewresearch.org/religion/2016/10/26/links-betwee... [2] - https://news.gallup.com/poll/1690/religion.aspx https://news.gallup.com/poll/1690/religion.aspx