The report is not entirely positive, however. To quote RAND DPRC’s summary:

The author could not determine whether this effect persisted over time, but he cited a different RAND study which observed that probationers randomly assigned to biweekly drug testing were less likely to have a full-time job during the twelve-month follow-up than those assigned to no testing. Thus, this new study raises fresh questions about the dynamic and differential effects of a common criminal justice practice.

The chart above shows that young black parolees did not show an increased likelihood to be employed or in school. While drug testing may increase overall likelihood for parolee success, parole violation for drug crimes must also exacerbate the revolving door approach to criminal justice.