Differential fertility makes society more conservative on family values

Abstract

Data from the General Social Survey indicate that higher-fertility individuals and their children are more conservative on "family values" issues, especially regarding abortion and same-sex marriage. This pattern implies that differential fertility has increased and will continue to increase public support for conservative policies on these issues. The association of family size with conservatism is specific to traditional-family issues and can be attributed in large part to the greater religiosity and lower educational attainment of individuals from larger families. Over the 2004 to 2018 period, opposition to same-sex marriage and abortion was 3 to 4 percentage points more prevalent than it would have been were traditional-family conservatism independent of family size in the current generation. For same-sex marriage, evolutionary forces have grown in relative importance as society as a whole has liberalized. As of 2018, differential fertility raised the number of US adults opposed to same-sex marriage by 17%, from 46.9 million to 54.8 million.

Keywords: cultural evolution; fertility; public opinion.

Fig. 1.

Traditional-family conservatism rises with family size, raising the representation of individuals from more conservative families. Bars are histograms that alternatively weight by the family of origin or by individual siblings within each family. (A) By number of siblings, adults ages 25 and above. (B) By number of children, adults ages 40 and above.

Fig. 2.

Religiosity and education mediate the association of sibship size with traditional-family conservatism. (A) By religious attendance, adults ages 25 and above. (B) By highest degree, adults ages 25 and above.

Fig. 3.

Unadjusted and adjusted associations of sibship size with traditional-family conservatism. Points are average marginal effects from probit models. Capped spikes are 95% CIs based on heteroskedasticity-robust SE. “Cohort, year” models adjust for quinquennium of birth and year of interview. See Materials and Methods for a description of additional covariates. Ed., education; rel., religiosity.

Fig. 4.

Composition effects of differential fertility on the prevalence of traditional-family conservatism. The deweighted share is computed by reweighting observations by 1 over sibship size. The absolute composition effect is actual minus deweighted share; the relative composition effect is absolute composition effect divided by deweighted share. Capped spikes are 95% CIs based on bootstrapped SEs. (A) Actual (solid) and deweighted (hollow) shares. (B) Relative (solid) and absolute (hollow) composition effects.