Gender, Genes, and Income: How Equality of Opportunity Changed in Norway Across the 20th Century

Abstract

Over the twentieth century, the gender gap in income has decreased dramatically. We study whether the relative importance of genetic and environmental influences for lifetime income changed as gender equalization took place. We use data on 11,677 twin pairs from Norway born 1915-1991, linked with individual-level administrative data on the full population's incomes in the period 1967-2016. Our results based on genetically sensitive variance decompositions shows that as social constraints inhibiting women from earning income waned over the century, the heritability of lifetime income increased over birth cohorts. Genetic influences matter more for men than for women, and non-shared environmental influences matter more for women than for men. This indicates that women still face structural constraints to a larger degree than men. Even in a welfare state like Norway where gender equality has been a political goal since the 1950s, equalization, as measured by the heritability of lifetime income, did not manifest itself to a high degree until the latest cohorts were established in the workforce (1981-1991). Our study shows the importance of considering historical developments of ascribed statuses such as gender when investigating genetic influences, and that genetics can serve as a prism through which to study social change.