Authors' reply

摘要

The discrepancy in the mean number of sexual partners reported by men and women has long been recognised,1 and not just in the context of Britain's National Surveys of Sexual Attitudes and Lifestyles (Natsal).2 The means should be identical if there are equal numbers of men and women in the population, and if all partners reside within the population. However, as analyses of the very first Natsal study show,1 these assumptions in practice do not hold true.