A recent study published in Scientific Reports suggests that political beliefs are increasingly linked to the number of children Americans choose to have. The findings indicate that while conservative individuals tend to maintain birth rates near historical averages, left-leaning individuals are having significantly fewer children. This demographic trend provides evidence that differing birth rates are a main driver of recent fertility declines in the United States.

The data revealed a pronounced change in how political beliefs relate to family size. For individuals born in the early 1900s, political orientation had almost no association with the number of children they had. However, beginning with the cohort born between 1943 and 1947, a massive divergence emerged.

“We expected these results, but not to such a dramatic extent,” Fieder told PsyPost. From the mid-century cohorts onward, individuals with right-wing political views maintained birth rates at or slightly above the replacement level. The replacement level, typically considered to be 2.1 children per woman, is the rate needed for a population to replace itself from one generation to the next without immigration.

In contrast, the birth rates of left-wing individuals dropped sharply, falling well below the replacement level in the more recent cohorts. The authors noticed this drop aligns with historical changes in family planning. “We found that the gap began with the introduction of modern contraception,” Fieder said.