About those, The Daily Mail writes:

The Home Office said the figures showed they were winning the fight against drugs.

But they could also be a warning that more drugs were getting in to Britain.

Street prices of heroin and cocaine have fallen sharply in recent years.

You’d think it might be a little tricky to get hold of evidence to bear that out, but it turns out that there’s a European street-drug-price index: the Price and Purity Information dataset from EMCDDA, the European Monitoring Centre for Drugs and Drug Addiction.

The latest year they have data for is 2006, but it bears the trend out: adjusted for inflation, heroin was 10% cheaper in 2006 than 2001, cocaine 20%, and Ecstasy had halved in price.

Anyone who watches The Wire can tell you that the drug market’s a bit more complex than that, though. Dealers have to make their cut.

We can get a proxy for that from the Home Office’s data. They break down, quarter-by-quarter, the purity of the drugs seized by HM Customs – the stuff which has been smuggled – and the purity of the drugs taken off the street by the police force. That tells another tale. Taking cocaine as an example:

while the purity of the cocaine smuggled into the UK has declined, from 71% to 63%, the drugs being seized by the police are now almost twice as adulterated as they were in 2001.

For heroin, however:

the dealers aren’t cutting their supply nearly as much; what they’ve been pushing has pretty much been what they’ve been being supplied with.

You could, and undoubtedly people will, write books on the reasons for this – sociological, economic, cultural. One thing it does suggest, though, is that there’s simply been more demand for cocaine: dealers have been stretching their supplies further to be able to sell to more of an eager public. Cocaine’s a party drug, a drug of affluence, ideal for the property bubble and market boom earlier this decade; maybe the credit crunch, which kicked in after this data was gathered, will trickle down in next year’s statistics…

As ever, the drug data collected here is available on Timetric for you to analyse yourself; let us know what conclusions you come to.