When it comes to drugs, it’s all about prices.

The ability to raise prices is– at least is perceived to be–a critical function of drug control policy. Higher prices discourage young people from using. Higher prices encourage adult users to consume less, to quit sooner, or to seek treatment. (Though higher prices can bring short-term problems, too, as drug users turn to crime to finance their increasingly unaffordable habit.)

An enormous law enforcement effort seeks to raise prices at every point in the supply chain from farmers to end-users: Eradicating coca crops in source countries, hindering access to chemicals required for drug production, interdicting smuggling routes internationally and within our borders, street-level police actions against local dealers.

That’s why this may be the most embarrassing graph in the history of drug control policy. (I’m grateful to Peter Reuter, Jonathan Caulkins, and Sarah Chandler for their willingness to share this figure from their work.) Law enforcement strategies have utterly failed to even maintain street prices of the key illicit substances. Street drug prices in the below figure fell by roughly a factor of five between 1980 and 2008. Meanwhile the number of drug offenders locked up in our jails and prisons went from fewer than 42,000 in 1980 to a peak of 562,000 in 2007.