A 1990 survey of one fifth of the prison population in the UK found that 30.8% of women and 22% of adult men had been regular drug abusers before conviction. Although only 3,000 of the 46,000 UK prison population were sentenced for drug offences in 1992, a 1993 study found more than 50% of those imprisoned used drugs within prison walls. One in eight of the drug abusers claimed the use of hard drugs, including amphetamines, LSD, tranquillisers, cocaine (crack), ecstasy and heroin. UK officials toy with the method used in the USA of detecting inmate drug abuse with urine analysis, at an estimated £12.5 per test. In the USA, greater than 85% of inmates in 1991 had a drug-related crime or a drug abuse history.