The shape of the distribution of the number of sexual partners.

Information on the number of sexual partners that people have is necessary for predicting the likely long term course of the AIDS epidemic. More information is required than is provided by simply stating the mean and variance of the number of partners. It is useful to find a family of curves which approximate data on the proportion of people in the various 'number of partners' categories. Two Australian surveys of the sexual behaviour of first year university behavioural science students were analysed. It was found here that log-normal distributions gave good approximations to the distribution of number of partners amongst people who had more than one partner. Gamma and negative binomial distributions gave less satisfactory fits and the truncated normal and Poisson distributions were clearly unable to match the data.