The proportion of variation attributable to different levels was calculated using the ‘latent variable’ approach to partitioning variation [35]. The adjusted model included age, sex, religion, place of residence, marital status, occupation type, educational attainment, household standard of living index, condom use at last sex, lifetime number of sexual partners, presence of sexually transmitted infection in previous 12 months, alcohol use during last sexual encounter, perception of HIV risk, and previous HIV testing.