Estimating hidden populations: a new method of calculating the prevalence of drug-injecting and non-injecting female street prostitution.

This paper outlines a new method we have developed for estimating the prevalence of streetworking prostitution and the proportions of female street-working prostitutes who are injecting drug users. This method is based on the capture/recapture approach and involves distinguishing new fieldwork contacts from repeat field work contacts. The size of the overall population can be modelled from records of the increasing ratio of repeat to new fieldwork contacts. The method may have a relevance beyond a concern with prostitution and drug injecting, and may be of value in estimating other hidden populations.