HIV, logic and sex in Africa.

A widely accepted explanation of the dramatically high rates of HIV infection in sub-Saharan Africa appeals to a supposedly distinct model of sexual partnering, referred to as 'multiple concurrent partnerships' or 'concurrency.' We discuss two problems with the concurrency explanation, and argue that it does not contribute to understanding the unusual rates of HIV infection in the region. We argue that there is no single 'concurrency hypothesis,' and the term 'concurrency' is imprecise and does not pick out an explanatorily distinct form of sexual behavior.