A study published at PLoS ONE 2(6): e543. doi:10.1371/journal.pone.0000543. "This paper provides strong evidence that when conducted properly, cross country regression data does not support the theory that male circumcision is the key to slowing the AIDS epidemic. Rather, it is the number of infected prostitutes in a country that is highly significant and robust in explaining HIV prevalence levels across countries." The article received several critical comments, including one by Halperin. The article's author John R. Talbott provides a very good rebuttal attacking the Africa trials' statistical analysis methodology.
Most every variable suggested to explain Africa's high prevalence rates fails the simple test of asking why other countries outside Africa have not had a similar experience. If circumcision is the key, why hasn't HIV/AIDS spread faster in those other non-African countries of the world that are predominately uncircumcised?