How many account for how much? Concentration of high‐risk sexual behaviour among Gay Men

Abstract

The data set of 2,182 gay/bisexual men's month‐long sexual diaries collected by the United Kingdom Socio‐sexual Investigations of Gay Men and Aids (Project SIGMA) was used to analyse the extent to which acts of anal intercourse (AI) are distributed among gay men, using the Lorenz/Gini methodology for measuring concentration. Most individuals (60%) who engage in AI do so only once or twice a month, but there is a long tail of those who do it much more. In terms of the amount of AI acts, one tenth of the individuals are performing half of the acts of AI. The Gini coefficient of concentration is high (0.55). Factors most affecting rates and concentration of risk behaviour include relationship status, HIV sero‐status and concordant/discordant partner status.