Nearly half of U.S. employers test job applicants and workers for drugs

From Discrimination and the Effects of Drug Testing on Black Employment by Abigail K. Wozniak.

Nearly half of U.S. employers test job applicants and workers for drugs. A common assumption is that the rise of drug testing must have had negative consequences for black employment. However, the rise of employer drug testing may have benefited African-Americans by enabling non-using blacks to prove their status to employers. I use variation in the timing and nature of drug testing regulation to identify the impacts of testing on black hiring. Black employment in the testing sector is suppressed in the absence of testing, a finding which is consistent with ex ante discrimination on the basis of drug use perceptions. Adoption of pro-testing legislation increases black employment in the testing sector by 7-30% and relative wages by 1.4-13.0%, with the largest shifts among low skilled black men. Results further suggest that employers substitute white women for blacks in the absence of testing.

I posted on this issue sometime in the past couple of years but can't lay my hands on the item. The point I was making in the older post is bolstered here - What makes sense (try to reduce the disparate impact of drug tests by race by outlawing such tests) from a logical and academic perspective can have dramatically counter-productive unintended outcomes in the real world. What this tentative evidence suggests is that drug tests are a way to increase opportunity, not suppress it.