”ASSORTATIVE MATING”: A genetic assessment of marriage markets

In traditional marriages, education of the spouse was the main attribute driving the benefits from marriage. But the sexual revolution transformed the ''marriage market'' towards ''hedonic'' marriages, those based on affinity of preferences and personality.

These are among the conclusions of research by Climent Quintana-Domeque and colleagues, to be presented at the Royal Economic Society''s annual conference in Bristol in April 2017. Their study focuses on ''assortative mating'' – the tendency of people with similar characteristics to marry each other – which may have direct implications for the transmission of socioeconomic status and inequality across generations.

The researchers note that economists and sociologists alike have a genuine interest in the correlation between spouses'' educational attainments. Whether this correlation captures assortative mating on education is still an open question.

By exploiting socioeconomic and genetic data from the Health and Retirement Study (a leading source for information on the health and economic wellbeing of adults over the age of 50 in the United States), this study illustrates how to combine quasi-experimental variation in spouses'' characteristics with a parsimonious matching model to investigate assortative mating.

The study uses a polygenic score (a single quantitative measure of genetic predisposition based on genetic variants present in the entire genome) that has been used to predict educational attainment in previous genetic research. Under a matching model with two characteristics, say education and anything else, the authors can test whether the spousal polygenic score has an effect on own educational attainment only through spousal education.

It turns out that they cannot reject this being the case. Given that polygenic scores are randomly assigned (genotypes are assigned randomly when passed from parents to offspring during meiosis) at least conditionally on genetic heterogeneity and population stratification, and they are relevant predictors of educational attainment, they can be used to isolate the variation of education that is uncorrelated with anything else.

The authors find that the degree of assortative mating on education can be quantified using correlation coefficients or standard regression techniques, at least among individuals who are on average 70 years old, who got married on average 40 years ago and have been married to each other ever since, and who are still alive.

Given that the polygenic score for education is likely to be correlated with ''things other than education'' (the anything else characteristic), the results are consistent with two potential explanations: first, things other than education (such as physical attractiveness) are irrelevant for marital attractiveness; second, things other than education are uncorrelated with education.

Whatever the reason is, the bottom line is that for a generation for whom education was (perhaps) the most important attribute in the marriage market, assortative mating on education can be assessed with standard regression techniques.

Traditionally, the main purpose of marriage was division of labour, and child rearing, rather than a hedonic marriage based on affinity of consumption preferences and personality. While it seems plausible to assume that in traditional marriages, education was the main attribute driving the benefits from marriage, the sexual revolution transformed the marriage market and its institution toward hedonic marriages.

''Assortative Mating: A Genetic Assessment'' (HCEO WP Series, 2016-034, December 2016) will be presented by Dr Climent Quintana-Domeque at the Royal Economic Society Conference, 2017. Dr Climent Quintana-Domeque is Associate Professor of Economics at the University of Oxford. Dr Nicola Barban is Senior Research Associate in the Department of Sociology at the University of Oxford. Dr Elisabetta De Cao is Postdoctoral Research Fellow in the Centre for Health Service Economics and Organisation at the University of Oxford. Dr Sonia Oreffice is Professor of Economics at the University of Surrey.