"In summary, of the almost 1.5 million arrestees at risk of drug abuse or dependence, 109,921 (about 7%) met drug court eligibility requirements. Of the 109,921 eligibles, approximately half (55,364) were actually enrolled in a drug court program. In aggregate, just 3.8% of the at-risk arrestee population was treated in drug court."

Source

Avinash Singh Bhati, John K. Roman, and Aaron Chalfin, "To Treat or Not to Treat: Evidence on the Prospects of Expanding Treatment to Drug-Involved Offenders" (Urban Institute: Washington, DC), April 2008, p. 33.
http://www.urban.org/...