The four categories of average total monthly income were defined by non-fixed quartiles for each follow-up. The adjusted odds ratios presented above were derived from a multivariate generalized linear mixed-effects model, which used the lowest category of average total monthly income as the reference category. The model also adjusted for age, female sex, unstable housing in the previous 6 months, engaging in sex work in the previous 6 months, drug dealing in the previous 6 months, regular employment in the previous 6 months and HIV status and included observations from December 1 1999 to December 30 2004.