Was it normal for Ms. Lasko to have expected fidelity from her longtime cohabiting partner? The answer is yes, according to the landmark 1994 National Sex Survey from the University of Chicago.
That survey of 3,500 people found that 94.6 percent of cohabiters and 98.7 percent of married people expected sexual exclusivity from their partners.
But the survey found that expecting fidelity didn’t mean getting fidelity, especially among unmarried people. Of married men, 4 percent said they had cheated on their wives in the past year. Of cohabiting men, 16 percent had cheated. And of single men with steady girlfriends, 37 percent had cheated.