A village has 100 men and 100 women. There is one impoverished male incel and one female sex worker. The other 99 couples are married.<p>The married women are faithfully monogamous. The married men all have sex with their wives and the sex worker.<p>People lie. The married men claim they are faithful. The sex worker claims she does not have any sexual relations, for fear of shaming and retribution from jealous wives.<p>Actual stats for sexual partners:<p>- men: mean ~2, mode 2, median ~2.<p>- women: mean ~2, mode 1, median ~1<p>Reported stats for sexual partners:<p>men & women all report: mean = mode = median = ~1<p>This implies a full survey, but then there is sampling. The sex worker probably doesn't have to lie. The chances are that even a large sample size of, say, 5% will not even include her.