Ronald Bailey digs through recent research:
In a September study in the Journal of Marriage and Family, [Stanford sociologist Michael Rosenfeld] uses time series data from the How Couples Meet and Stay Together survey (HCMST) to probe the longevity and breakup rates of America’s marriages. The HCMST, which began in 2009, is a nationally representative survey of 3,009 couples, of which 471 are same-sex. Rosenfeld’s paper reports the breakup rate of the couples surveyed annually through 2012.
What he discovered:
Not too surprisingly, there are big differences in relationship stability between married and unmarried heterosexual couples. The annual breakup rate among married different-sex couples was 1.5 percent. The relationships of unmarried different-sex couples dissolved at annual rate of 21.7 percent.
Married same-sex couples broke up at a rate of 2.6 percent per year, while 12.8 percent of unmarried same-sex couples went their separate ways annually. Interestingly, Rosenfeld notes that “lesbian couples have a significantly higher rate of break-up compared to heterosexual couples, while gay male couples have a break-up rate that is not distinguishable from the break-up rate of heterosexual couples.” It is also noteworthy that unmarried same-sex couples broke up at about half the rate of unmarried different-sex couples. It is likely that part of the reason for this disparity is that unmarried same-sex couples had already been together almost twice as long their different-sex counterparts at beginning of the survey.
Rosenfeld also found that “marriage is not just associated with stability but causes it.”