The Cohabitation Gap: Context Matters, But Perhaps Less Than Scholars Think

Are there contexts where cohabitation is more like marriage than in others? Of course. If a New Hampshire couple lives together for at least three years before one of them dies, the surviving partner has all the same rights as if they had been legally married. Similarly, common law marriages commenced in 2016 or earlier are recognized in Alabama. However, an Alabama couple that moved in together in January 2017 or later has neither the rights nor  responsibilities that the state associates with marriage. Context matters, even in the same place at different times.

Nonetheless, it seems to us that scholarship on differences between married and cohabitating couples tends to overestimate the extent to which these differences can be expected to shrink over time. In particular, the importance of the prevalence and acceptance of cohabitation seems to be overestimated. Here we use Ann Evans and Edith Gray's recent work on Cross‐National Differences in Income Pooling among Married and Cohabiting Couples to explain how different assumptions stand up to empirical testing (although their work is hardly the only scholarship anticipating cohabitation gaps to close as living together becomes more common).

In most countries, there exists a "cohabitation gap," wherein cohabiting couples are less likely to pool their incomes, or act as an economic unit, than married couples. Evans and Gray assembled data across countries to test the ways in which context conditions the size of the cohabitation gap in income pooling. Their analysis allowed them to describe contexts in which marrieds and cohabitants behaved more similarly, as well as contexts where the cohabitation gap was large.

Their hypothesis that legal structure matters was fully supported by the data. They distinguished taxation policies that: 1) taxed everyone as an individual, regardless of marital status; 2) taxed everyone as an individual, but treated married couples differently in some respects; and 3) taxed married couples on their joint income, while taxing cohabiting couples as individuals. They expected that joint taxation would accentuate the tendency for married couples to pool income more often than cohabiting couples, and that is exactly what they found. When the law treats couples differently, they behave differently.

Evans and Gray's work also illustrates a more complicated way that context matters: countries differ in how much cohabitation reflects economic disadvantage. There is a vast amount of literature establishing that negative selection into cohabitation varies across countries, but Evans and Gray went a step further to quantify that difference: they developed a measure of the extent to which cohabitation reflected a "pattern of disadvantage." They then used their measure to explain cross-national variation in the size of the cohabitation gap. 

They found that in contexts where cohabitation is "a poor man's marriage," income pooling in cohabitation comes closer to the levels seen in marriage. Economic disadvantage motivates income pooling—doing everything necessary to get by. Further, poor couples might not have separate savings simply because they do not have savings. Cohabiting couples looked more like married couples in their amount of income pooling in countries with a strong pattern of disadvantage, and they looked less like married couples where income differences by legal union status were less pronounced. Context matters because it shapes which couples cohabit. It isn't that cohabitation is more marriage-like when the pattern of disadvantage is strong; rather, it is that low socioeconomic status is a common cause of both cohabitation and income pooling.

However, Evans and Gray's analysis did not support their expectation that where cohabitation is prevalent and accepted (or socially normative), the cohabitation gap in income pooling will be smaller. They call this the evolutionary hypothesis due to the manner in which cohabitation diffuses and evolves over time and different groups. Their hypothesis is in keeping with Kathleen Kiernan's influential work describing the evolution of cohabitation in four stages in Western Europe. Kiernan explained how cohabitation first existed as an adaptation to the legal complexity and financial hurdles of obtaining a divorce (as a substitute for remarriage), and it was a means of forming an initial union only among small subgroups (e.g., those protesting the church's monopoly on marriage, and those too poor to marry). Cohabitation did not emerge as a prelude to marriage (or a testing phase for it) until the 1970s, and children were still considered appropriate only to marriage. In the third stage, fertile cohabitations become socially acceptable, and in the fourth stage, marriage and cohabitation are considered indistinguishable partnership alternatives. 

This evolutionary view contributes to the belief that cohabitation gaps—whether they be in income pooling or childbearing or relationship stability—should shrink over time. But Kiernan herself also emphasized that the four stages can and do exist within the same society. For example, cohabitation can be a trial marriage for some, while being a marriage substitute for others. This means that even in countries where some cohabitations and marriages are virtually indistinguishable, there will be other cohabitations better characterized by stages 1-3, and thus quite different from marriage.

We argue that evolutionary hypotheses are misguided to the extent that they neglect the heterogeneity within countries that are more “advanced” in the partnership transition. In other words, just because some marriages and cohabitations have become virtually indistinguishable in some societies is no reason to believe that cohabitations on average will be indistinguishable from marriages on average in any society. This would explain why Evans and Gray's data showed that the prevalence of cohabitation did not condition the size of the cohabitation gap in income pooling. On average, married people were more likely to act as an economic unit regardless of how common cohabitation had become among their peers.

Laurie DeRose is a senior fellow at the Institute for Family Studies, Assistant Professor of Sociology at the Catholic University of America, and Director of Research for the World Family Map Project. Anna Barren is a graduate of the Philosophy program at Christendom College and is the administrator of the Sociology department at the Catholic University of America.