The U.S. marriage rate has hit a record low, according to the Good Men Project. About 57% of adults got married 10 years ago, but only 51% are getting married now.

Researchers think they know why.

A new study shows women are happier when they don’t have children or a husband to go home to. That same study shows men are happier and healthier when they are married.

Paul Dolan, a professor of behavioral science at the London School of Economics, said the latest evidence showed that the traditional measure of success has changed and happiness is no longer correlated with being married and raising children.

“We do have some good longitudinal data following the same people over time, but I am going to do a massive disservice to that science and just say: if you’re a man, you should probably get married; if you’re a woman, don’t bother.

Dolan says men benefited from marriage because they were much calmer. He added that marriage puts more stress on women and they die sooner as a result.

“[Men] take less risks, you earn more money at work, and you live a little longer. She, on the other hand, has to put up with that, and dies sooner than if she never married. The healthiest and happiest population subgroup are women who never married or had children,” he said.

Dolan’s latest book, Happy Ever After, cites evidence from the American Time Use Survey (ATUS), which compared levels of pleasure and misery in unmarried, married, divorced, separated and widowed individuals, according to The Guardian.

Dolan says men showed more health benefits from settling down, but middle aged married women are at higher risk of physical and mental conditions than single women.

“You see a single woman of 40, who has never had children – [you say] ‘Bless, that’s a shame, isn’t it? Maybe one day you’ll meet the right guy and that’ll change.’ No, maybe she’ll meet the wrong guy and that’ll change. Maybe she’ll meet a guy who makes her less happy and healthy, and die sooner.”

When the study was initially published in a London newspaper, the comments section was filled with angry wives and mothers who disagreed with his findings.

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