America’s birth-rate decline is being largely driven by people with left-wing beliefs, according to new research.
A study published in Scientific Reports suggests political beliefs are tied to the number of children Americans choose to have,.
People with left-wing beliefs tend to have fewer children, whereas conservatives maintain birth rates closer to historical averages.
“In a previous study, we demonstrated that these fertility differences are likely to contribute to a gradual demographic shift toward more conservative societies in Europe,” one of the lead authors of the new study, Martin Fieder, said.
“In the present study, we wanted to determine when this divergence in fertility first emerged.”
Scientific news website Psypost explains, “To explore these trends, the scientists analyzed data from the United States General Social Survey collected between 1970 and 2022. The sample included 22,975 adults, consisting of 10,681 men and 12,294 women. All participants were over the age of 40, meaning they had generally completed their childbearing years.
“The participants were grouped into 16 birth cohorts based on five-year intervals. This started with those born between 1903 and 1907 and ended with those born between 1978 and 1982. The researchers measured political orientation using a seven-point scale ranging from very left to very right, grouping these responses into three broader categories representing left, center, and right orientations.
“To evaluate how fertility impacts the spread of political traits over time, the researchers used a statistical tool often applied in evolutionary biology to measure phenotypic selection. This method allows scientists to measure how strongly a specific observable trait influences reproductive success.
“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.”
From the middle of the 20th century, conservatives were able to maintain birth rates at or slightly above replacement levels—the level needed for a population to maintain stable numbers—but the birth rate for left-wingers declined sharply.
The authors noted that the fall coincided with the introduction of modern forms of contraception.
Other lifestyle factors also strongly influenced fertility.
Education was consistently linked to lower fertility, while religiosity was linked to higher fertility.
“Our findings suggest that differences in fertility rates across the political spectrum may gradually change the political composition of the US population over time,” Fieder said.
“In particular, the decline in overall fertility appears to be driven largely by the sharp decrease in births among individuals left of the political center, possibly since the widespread use of modern contraceptives, although our data cannot directly prove this mechanism.”
