How were the data for estimating the size of the injecting drug user (IDU) population inaccurate?
There were two problems with the data we used for the size of the IDU populations. First, we used the population rate of IDUs in each of the metropolitan statistical areas (MSA) reported in Brady et al (2008) to multiply by the MSA population size to get an estimate number of IDUs in each of the MSA. During this process, the population size that was used for San Juan, PR, was only for the municipio (city) of San Juan, and not the entire MSA. Secondly, we originally used data from Brady et al. for the year 1999 (before MSA definitions changed); during re-analysis, we determined that the 2002 estimates, which were closer to the time of the NHBS data collection, would be a more accurate estimate of population size for our purposes. The data used in the revised report for the injecting drug user population size in each MSA come from the online appendix available with electronic versions of the Brady et al. paper. Reference: Brady JE, Friedman SR, Cooper HL, Flom PL, Tempalski B, Gostnell K
