Another possible explanation for increased awareness in our analysis is that, for some reason, MSM with diagnosed HIV infection were more willing to disclose their HIV status to interviewers in 2011 than in 2008. NHBS operational procedures and questions regarding HIV status did not change between 2008 and 2011. However, participants may have been more open about their status in 2011 if stigma associated with HIV infection or homosexuality is decreasing, for which some evidence exists [23,24].