Over all cities and years, the cluster-adjusted mean price for heroin was 1.09 (se=0.12) US dollars ($) per milligram-pure (mg-pure). Seattle had the highest mean price at $4.68/mg-pure, while San Diego had the lowest mean price at $0.22/mg-pure. lists the mean price, maximum price and minimum price for each MSA along with the years that those prices occurred. With the exception of San Francisco, each MSA’s maximum price was recorded before the minimum price. The smallest change between the maximum price and the minimum price was a 60% reduction in the cost of heroin recorded in Dallas. San Diego saw the largest decrease, with the purity-adjusted price of heroin falling 89% between 1996 and 1999. Over the course of the study period, the mean inflation-adjusted price of heroin dropped 62% from $1.67 to $1.03/mg-pure.
Price and purity of heroin, 1993 – 2004
also displays information on the changes in the purity of heroin in each of the MSA regions between 1993 and 2004. The cluster-adjusted mean purity of heroin was 34.33 (se= 3.56) percent heroin by weight (%). Changes in the purity of heroin by MSA were less consistent than changes in the price of heroin during the study period. Half of the MSAs had minimum purity values occurring before the maximum purity during this time. However, the other half of the MSAs saw reductions or wide fluctuations in the purity of samples collected: Boston, Chicago, Houston, Los Angeles, New Orleans, New York, Philadelphia, San Francisco, Seattle, and St Louis.
shows the changes in the price and purity of heroin averaged per year. Consistent with the results presented in , the price of heroin decreased dramatically between 1993 and 1997 and stabilized thereafter. The yearly averaged purity graph shows a substantial increase from 1993 to 1998 with a subsequent decline.
Mean price and purity of heroin samples between 1990 and 2004
shows the changes in the percent of heroin coming from South America, SWA, SEA and Mexico. MSAs were organized into two regions based on predominance of specific heroin sources: east and west of the Mississippi River. East of the Mississippi River, heroin from South America predominates and the median percent of heroin from South America grew at a significant rate of approximately 7% per year in absolute terms across all eastern MSAs. Percent of samples from SEA and SWA declined significantly in several eastern cities. West of the Mississippi, Mexican heroin predominates with three cities showing small, but significant increases in percent of Mexican heroin. No South American, SEA, or SWA heroin was recorded in cities west of the Mississippi.
Geographic origin of heroin and percent change (absolute) between 1993 and 2004
shows the yearly changes in the geographic origin of heroin collected by DEA agents. This graph visually displays the results presented in . The percent of South American heroin in the US market increased remarkably between 1993 and 2004, while the percent of SEA heroin decreased almost to 0% of the US market. Mexican heroin stayed relatively constant.
Geographic source of heroin samples between 1990 and 2004
In order to test if time and percent South American heroin predict price and purity nationally, multilevel growth curve models with years nested in MSAs were estimated. Out of a possible 240 units of MSA-years, 221 units had complete price and covariate data (mean: 11.1 years per MSA). shows the results for the 4 models predicting the inflation-adjusted price of heroin controlling for other MSA covariates. Of the four models, the full model is the best fitting. These models suggest that both the effect of time and the percent of heroin from South America are quadratic and statistically significant independent predictors of lower heroin prices. These models confirm that the quadratic price curve presented in is statistically significant. The full model suggests that price of heroin decreased $0.26/mg-pure per year on average, but that this effect tailed off as time increased. Similarly, for each 1% increase in heroin coming from South America the price of heroin decreased $0.01/mg-pure (e.g., each 10% increase in South American heroin produced a $0.13/mg-pure price decline). This effect also asymptotically tailed off as the percentage of South American heroin increased. None of the other MSA level covariates had a significant effect on the price of heroin, including the percentage of heroin originating in Mexico.
Price of heroin (cents/mg) between 1993 and 2004
In an analysis not shown, we restricted the full price model to the years 1993 to 1999 when the largest increase in percent of SA heroin and decrease in prices occurred. During this time, each 10% increase in SA heroin resulted in a $0.20 (p < 0.01) decrease in the price per mg-pure. For these 7 years, the percent of heroin originating from SA increased by 34%, resulting in a model-imputed decrease of $0.66/mg-pure due to changes in the geographic origin of heroin alone.
shows the models predicting the change in purity. Out of a possible 240 units of MSA-years, 221 units had complete purity and covariate data (mean: 11.1 years per MSA). From 1993 to 2004, the purity of heroin did not show a statistically significant linear or quadratic change over time after adjusting for the percent of heroin originating from South America and other covariates. Increases in the percent of heroin originating from South America resulted in a linear increase in the purity of heroin in US markets. Each 10% increase in the amount of heroin originating in South America produced an absolute increase of 1.7% in the purity of heroin. Unlike the price model, the effect of South American heroin on the purity of heroin was not quadratic. Again, the percentage of heroin originating from Mexico had no effect on the purity of heroin. The percentage of adults and males in an MSA had a statistically significant effect on the purity of heroin, but no other MSA covariates showed effects on the purity of heroin in an MSA.
Purity of heroin between 1993 and 2004