drug users, for whom it could plausibly be claimed that they “needed” to commit property crimes to finance their drug usage.

In contrast, in their report for the British Home Service, Godfrey, et al. (2002) assume that all property crime associated with problem users is caused by drug use. Problem users are defined as _all_ users of opiates or crack cocaine (as opposed to only addicted users). The crime attributed to problem users is based on a longitudinal study of patients in drug treatment programs, reported in Gossop et al. (2001), and is the amount by which these patients reported reducing their criminal activity from the three months prior to intake to the period 9-12 months after entering treatment. Godfrey, et al. (2002) conclude that the entire reduction can be attributable to the reduction in drug use and assume that reductions would be similar if all nontreated problem drug users were also to reduce their consumption. This estimate is likely to be severely upwardly biased, however. First, both crime and drug use are the product of unobserved individual proclivities; drug treatment addresses these proclivities. The observed association between drug use and crime is therefore likely to be spurious, driven by the direct effect of treatment on crime rather than its indirect effect on crime through reduced drug use. Second, problem users who enter treatment are more likely than other users to have committed crimes in the first place, again biasing upwards the amount of crime that can be attributed to _all_ drug users.

Estimates of the number of problem users are controversial. In principle, they are those for whom drug use is “no longer controlled or undertaken for recreational purposes and where drugs have become a more essential element of the individual’s life” (Godfrey, et al. 2001, p.2). In practice, standards for estimating the fraction of problem users among all users, and the fraction itself, vary widely. In the Godfrey, et al. study, problem users in England and Wales are all crack or opiate users, and are estimated to be at about 15 percent of all (class A drug) users. This is below the fraction of cocaine and crack users among all drug users in the United States (about 19 percent from the HHS estimates reported above), but higher than the 6 percent of drug consumers who are regarded as problem users in the US, according to the estimates reported in Reuter (2001) of two million people.

Existing analyses reveal significant uncertainty about the tangible social costs of drug use. It seems unlikely, given significant upward biases in the measurement of costs, that they actually exceed 0.5 percent of GDP, but the possibility that they are as much as one percent of GDP cannot be excluded. The victim costs of crime by addicted drug users are surely higher than the $200 million estimated by the White House, but also likely to be only a fraction of the more than ₤12 billion estimated for the British Home Office. Other social costs (e.g., those from reckless driving, or intra-family abuses committed by drug users) have not been estimated at all, although these are likely to be low compared to the same costs imposed as a result of alcohol abuse.

These calculations leave out the intangible social costs of drug use – the costs that, in fact, may actually be driving drug policies in some countries. Social norms are in some places so strong and social opprobrium regarding drug use so great that the tangible social and private costs of drug production may be irrelevant in the evaluation of drug policies. Instead, policy debate is driven by the disutility that non-users feel from having drug users in their midst.<sup>3</sup> Such a social reaction is often culturally rooted and may bear no relationship to the tangible 3 It may also be the case that prohibition is favored because the largest domestic costs of prohibition are borne by groups that have less political influence (e.g., residents of inner cities).

10