What does the GSS data actually show about infidelity by gender?

Lifetime infidelity prevalence: men vs women

GSS data, aggregated across multiple survey waves, shows lifetime infidelity prevalence of approximately 20% for men and 13% for women. These figures capture sexual infidelity as defined by the respondents themselves. Broader definitions that include emotional affairs, sustained intimate contact outside the relationship, and non-physical romantic involvement push the combined figure toward 25% of adults.

Both numbers are self-reported and subject to social desirability bias. The sensitive nature of the topic means underreporting is expected in both directions, though the extent differs by gender, cultural context, and survey format. The true prevalence is almost certainly higher than the GSS figures suggest.

The gender gap is closing in younger cohorts

One of the more striking recent findings in the GSS data is the near-total inversion of the gender gap among adults under 30. In the 18 to 29 age cohort, women now slightly exceed men in self-reported infidelity (11% versus 10%), reversing a historical pattern that has held across most prior survey decades.

Researchers propose several mechanisms. Increased female financial independence reduces the economic constraints that historically made infidelity riskier for women. Equalised access to digital platforms and dating apps has created new opportunity structures. And shifting cultural scripts around female sexual autonomy appear to be reducing the social stigma asymmetry that previously suppressed female disclosure. The convergence is most pronounced in urban, higher-education cohorts and appears less pronounced in older age groups, where the traditional gap remains wider.

Affair type distribution by gender

The Institute for Family Studies iFidelity Survey (Wang, 2020; YouGov, n=2,000 ever-married U.S. adults) found that among those who reported having an affair, the combined physical-and-emotional type was the most common for both genders. The headline finding challenges the popular assumption that men primarily have physical affairs and women primarily have emotional ones: the purely physical affair is a minority experience even for men.

The gender stereotype holds directionally, with men dominating sex-only affairs, but the combined type is more common than purely physical or purely emotional affairs for both genders. Among all ever-married adults who reported cheating, roughly 45% described a combined affair, 32% an emotional-only affair, and 23% a sex-only affair.

Motivational differences by gender

Glass and Wright 1985/1992 (Journal of Marriage and Family) identified persistent motivational gender differences across their research samples. Men cited sexual gratification as the primary motivator in approximately 75% of cases. Women cited falling in love with the affair partner in approximately 77% of cases, with 55% also citing sexual motivation compared to 75% of men. These findings have been replicated in subsequent research with broadly consistent directional findings, though the exact percentages vary across studies.

The motivational data does not establish exclusive categories. People who cheat for primarily sexual reasons can also develop emotional attachment; those who begin with emotional connection frequently proceed to physical involvement. The high prevalence of combined affairs in the IFS data reflects this overlap.

The Age-9 phenomenon

Alter and Hershfield 2014 (PNAS, n=8 million users from the Ashley Madison dataset) found that individuals at ages 29, 39, 49, and 59 are 18% more likely to be actively seeking affairs than at any other age. The pattern holds across both genders, though it is slightly less pronounced in women.

The researchers attribute this to heightened mortality salience at the approach of a new decade: the existential weight of turning 30 or 40 produces identity-seeking and meaning-seeking behaviour that, for some people, expresses as relationship disruption or exit-seeking. This is a population-level statistical finding, not a prediction for any individual person.

Data caveats

All GSS infidelity figures are self-reported and almost certainly underestimates. Social desirability bias in survey research is well-documented, and infidelity is a high-stigma behaviour. Different studies use different definitions of infidelity, creating variation across published prevalence figures. The GSS captures a U.S. representative sample; rates in other countries and cultural contexts will differ. Prevalence figures also change across survey cohorts as cultural norms shift, which is precisely why the under-30 gender gap closure is significant: it represents a genuine generational change in reported behaviour.