A lifetime portfolio of risky and risk-free sexual behaviour and the prevalence of AIDS.

A lifetime portfolio of risky and risk-free sexual activities is conceptually constructed in this paper. People's time allocation between risky and risk-free sexual activities affects, and is affected by, the prevalence of AIDS. A small satisfaction differential between risky and risk-free sex can lead to a significant prevalence of AIDS. Numerical simulations suggest that the reduction in the prevalence of AIDS generated by a 1% improvement in the sensual quality of freely distributed condoms can be 0.855% when the initial satisfaction differential between risky and risk-free sex is 50% or 0.464% when the initial satisfaction differential is 100%.