Case studies by industry (as published by Working Partners of the United States Department of Labor):

	Retail
	Hospitality Industry
	Manufacturing
	Wholesale

A National Institute on Drug Abuse (NIDA) study found that drug-using employees were:

	2.2 times more likely to request early dismissal or time off
	2.5 times more likely to have absences of eight days or more
	3 times more likely to be late for work
	3.6 times more likely to be involved in a workplace accident
	5 times more likely to be injured in an accident off the job, which affected attendance or job performance
	5 times more likely to file a workers' compensation claim

Source:

Backer, Thomas E,  Strategic Planning for Workplace Drug Abuse Programs, National Institute on Drug Abuse (NIDA), 1987, p.4.

The United States Postal Service

The US Postal Service would have saved $52 million by 1989 had it screened out all the drug-positive postal service applicant's in 1987.  By June of 1991 this figure more than doubled ($105 million).  Employees testing positive on their pre-employment drug tests were 77% more likely to be fired in the first three years of employment, and were absent from work 66% more often.  37% of the positive testers had been disciplined one or more times during their three years of employment verses 19% of the negative testers.

Source:

Pre-Employment Drug Testing:  Associations with EAP, Disciplinary, and Medical Claims Information, United States Postal Service Personnel Research & Development Branch Office of Selection and Evaluation, July 1992.

Southern Pacific Railroad

Southern Pacific implemented reasonable-suspicion testing  with a 22.9% positive rate in 5 months.  Three years later, the rate dropped to 5.8%.  Testing was expanded to include post-accident and as a part of a regularly scheduled physicals.  Personal injuries and accidents have dropped dramatically: 71% for injuries and 88% for train accidents due to human failure.

Source:

Taggart, Robert W.  "Results of the Drug Testing Program at Southern Pacific Railroad," Drugs in the Workplace:  Research and Evaluation on Data, National Institute on Drug Abuse (NIDA), Rockville, MD, 1987, pp. 97-108.