"Overall, the number of PWID per 10,000 persons aged 15–64 years varied from 31 to 345 across MSAs [Metropolitan Statistical Areas], median 104.4 (mean 127.4; standard deviation 66.7; percentile range 76–162) in 1992 and from 34 to 324 across MSAs, median 91.5 (mean 103.6; standard deviation 56.4; percentile range 61–125 ) in 2007 indicating an overall decline in PWID prevalence across MSAs.

"Figure 5 shows the overall trajectory of the PWID prevalence rates based on the multilevel model. Trend analysis of the overall results is consistent with a decline in the early study period, followed by an increase in 2000–02, and then remaining stable thereafter over time. On average there has been very little change since 2002 (mean 105.0) to 2007 (mean 103.6). Overall, across the 96 MSAs the mean PWID prevalence mostly decreased during our study period, as did the dispersion of estimates over time."


Tempalski B, Pouget ER, Cleland CM, Brady JE, Cooper HLF, et al. (2013). Trends in the Population Prevalence of People Who Inject Drugs in US Metropolitan Areas 1992–2007. PLoS ONE 8(6): e64789. doi:10.1371/journal.pone.0064789