"Increased admissions to drug treatment are associated with reduced incarceration rates. States with a higher drug treatment admission rate than the national average send, on average, 100 fewer people to prison per 100,000 in the population than states that have lower than average drug treatment admissions. Of the 20 states that admit the most people to treatment per 100,000, 19 had incarceration rates below the national average. Of the 20 states that admitted the fewest people to treatment per 100,000, eight had incarceration rates above the national average."
Justice Policy Institute, "Substance Abuse Treatment and Public Safety," January 2008.