The global War on Drugs has failed, as illegal drugs have only become cheaper, more abundant and more pure in recent decades, according to a report published by a group of U.S. and Canadian researchers on Monday in the British Medical Journal.

“The punitive prohibitionist approach to global drug control has proven remarkably costly, ineffective and counterproductive,” said Ethan Nadelmann, director of Drug Policy Alliance, following news of the report.

“It has generated extraordinary levels of violence, crime and corruption while failing to reduce the availability and use of psychoactive drugs.”

According to the report, in the U.S. the average price of heroin, cocaine and cannabis decreased by roughly 80% between 1990 and 2007. Average purity increased by 60%, 11% and 161% respectively.

Meanwhile, seizures of cannabis by the U.S. Drug Enforcement Administration increased by 465% between 1990 and 2010 and heroin seizures increased by 29%. Cocaine seizures fell by 49%.