Monogamy“You’re the one for me.” For many, maybe most of us, that feeling rings true—the romance of two people, two alone, whether “till death do us part” or serial monogamy.

In heterosexual marriages, 45 to 55 percent of married women and 50 to 60 percent of married men cheat, recent studies say. That means around half of heterosexual couples stay sexually monogamous. Other studies report higher rates—a U.S. survey from 1997 found 77 percent of married men and 88 percent of married women successfully practiced monogamy in marriage.

In gay relationships, figures differ. One 1991 study reported only 17 percent of gay men in steady relationships did not have sexual encounters outside the partnership. But in a U.S. study from 1999 looking at gay male couples who’d gone through a commitment ceremony, more than 80 percent said they were monogamous. Researchers say gay male couples often use “monogamy” to mean “emotional monogamy” rather than sexual fidelity.

Lesbian couples in a 1983 study reported 72 percent had monogamous relationships. A study from 2007 reports that lesbian relationships of all studied are most likely to be monogamous, followed by heterosexual relationships, followed by gay male relationships.

How many people are coupled up, then? In 2005-2007, about 55 percent of the United States’ adult population was married. Of the unmarried, another 11 percent lived with partners, including partners of the same sex. So about two-thirds of us live as couples. Of that two-thirds, a significant portion practice monogamy.

Whatever monogamy means to you, there’s a strong likelihood you have had, do have, or will have a monogamous relationship in your life.