Association of HIV and skewed male:female ratios supports effect of such ratios on partner concurrency.

<p>M:F ratios were calculated as the total number of male individuals aged 18–64 divided by the total number of female individuals aged 18–64 for each city. Groups were established as deviating >0.05 from the mean M:F ratio (0.97) and <i>p</i> values are for T-tests between extremes (n = 24 for <0.92 and 13 for >1.03) and mid-range (n = 43). <b>A.</b> Total reported HIV incidence per city varies by M:F ratio, but not significantly. <b>B–C.</b> HIV incidence reports amongst (<b>B</b>) males and (<b>C</b>) females exposed by heterosexual contact. <b>D–E.</b> HIV incidence among (<b>D</b>) black or (<b>E</b>) white individuals. <b>F.</b> HIV incidence reports by MSM exposure only, as a percentage of estimated number of GLB individuals per city. Bars = SEM.