Single motherhood might indeed be easier today than before. But all these comments miss the point. The major trend isn’t a rise in single parenthood; it’s a decline in the formality of marriage. People still couple up. They still live together. They still have sex, rear babies, and pool resources. They’re just not getting married. They’re not subjecting their relationships to the bundle of rights and responsibilities that governments call ‘marriage’. As the Icelandic demographer Ari Klængur Jónsson clarified in his report ‘A Nation of Bastards?’ (2019), the vast majority of nonmarital births in Iceland are not to single mothers; they’re to cohabiting couples.

For demographers, the rise in cohabitation is at the centre of the marriage revolution. The numbers are staggering. In the US, the number of heterosexual cohabiting couples rose from 1.6 million in 1980 to 8.5 million in 2018. In Norway, a third of respondents in 1984 thought it was OK for an unmarried couple to live with children; by 2007, more than four in five approved of cohabitation without a plan to marry. ‘Unprecedented changes in the timing, duration, and sequencing of intimate coresidential relationships have made the study of marriage far more complex today than in the past,’ begins a recent scholarly review from Cornell University in New York. ‘The rise in cohabitation is the major reason why.’

To explain the decline of marriage, we shouldn’t look at single parenthood and weakening pair-bonds. We need to look at cohabitation.