Advantages and challenges of using census and multiplier methods to estimate the number of female sex workers in a Chinese city.

Using census and multiplier methods to estimate the size of the population of female sex workers (FSWs) in a small city in western China, this study compared the advantages and challenges of the two methods. It was estimated that there were about 1,500 FSWs within the urban area using the census method, which was significantly lower than that estimated by the multiplier method (2,500). Each method has advantages and limitations, and could be applied to different situations. The census method is less time and resource consuming in smaller regions and has a tendency to underestimate, and therefore, the result can be viewed as a low limit. It is useful in a local setting, for example, when estimations are needed for planning HIV/AIDS prevention programmes in a single city. Using existing information or resources, multiplier method could be used to produce estimates for a large geographic area or at a national level.