- Political orientation correlates with fertility, with implications for long-term ideological shifts.
- Earlier US cohorts (1898-1942) show little fertility difference by political orientation.
- From the 1943-1947 birth cohort onward, right-wing individuals maintain near or above replacement fertility, while left-wing fertility declines sharply below replacement.
- Selection gradient analyses indicate increasing directional selection favoring right-wing orientation over time.
- Education consistently negatively associates with fertility, and religiosity shows positive but weaker effects.
- The strong association between political orientation and fertility in recent cohorts is only observed among White Americans, not Black Americans.
- Fertility decline in the United States is disproportionately driven by left-leaning individuals.