They live in a liberal-run society that doesn't believe in abstaining from sex

Look at California cities like SF

Conservative have higher fertility rates than liberals, and fertility rates are lower in urban areas like SF than they are in rural areas.

https://www.aei.org/articles/the-conservative-fertility-advantage/

https://www.usnews.com/news/healthiest-communities/articles/2018-10-17/as-fertility-rates-fall-across-us-gap-widens-between-rural-and-urban-counties