The Home Office have published a research study called The economic and social costs of Class A drug use in England and Wales which provides a useful analyses of the wider costs of illegal drugs – the most thorough and recent such study available. The study, undertaken by York University, explains it's methodology and has analysis which is very clear about it's limitations, giving a wide margin of error on all its estimates due to the unreliability of some source data.
The study estimates the total social costs of Class A drugs in England and Wales, 2000 to be between £10.4bn to £17.4bn, with a medium estimate of £12bn. These costs include direct government expenditure as well as addition costs incurred by unemployment, criminal justice, heath problems and social services.
An updated version of study published in 2006 estimates the economic and social costs of Class A drug use to be around £15.4 billion in 2003/04, with an associated confidence range of between £15.3 billion and £16.1 billion. Due to methodological and data improvements, the results for 2003/04 are not comparable to those for 2000. The study estimates that 327,466 problematic users are responsible for 99% of these costs, which equates to £44,231 per year per problematic drug user. The study also notes that drug-related crime costs account for 90 per cent of costs associated with problematic drug use.
The Prime Minister's Strategy Unit has also produced a Drugs Report which includes estimates for the costs caused by high-harm-causing drugs (ie crack cocaine and heroin). This is a PowerPoint style presentation which cites sources but does not explain the methodology used to obtain its "Team analysis" data.
In Phase 1 – Understanding the Issues, the Strategy Unit report says that the cost of damage to health and social functioning of heroin and/or crack users arising from use is £5bn. This does not include the cost of drug related crime, which the report looks at separately.
For the cost of drug related crime, the report says that drug users are estimated to commit 36m drug-motivated crimes each year, 56% of the total number of crimes, and that drug-motivated offences are estimated to be responsible for a third of the total cost of crime (£19bn). This cost includes security expenditure, property stolen, emotional impact on victim, lost output and expenditure on criminal justice system.
The fact the over half of all crime is drug motivated, but only a third of the cost of crime is a result of drug motivated crime, is due to drug motivate crime being more likely to involve "medium trauma" crimes (burglary, theft or/from vehicles, common assault) and less likely to involve "high trauma" crimes (violence, sexual, robbery) compared to non-drug motivated crime.
The report also goes into detail about the criminal behaviour of the 280,000 high harm drug users who it says are using heroin and/or crack at one time. According to the report, these high harm users are responsible for 87% of drug motivated crime costing £16bn, and that the highest 10% offending heroin and/or crack users are estimated to be responsible for crime costing over £365,500 per user per year.
Nearly half of high harm users are arrested each year and a quarter of high harm users likely to be in prison at any one time.