Do Drug Arrests Work?

The Effectiveness of Drug Enforcement in Europe

By Beau Kilmer, Stijn Hoorens, and Jonathan P. Caulkins

Beau Kilmer is codirector of the RAND Drug Policy Research Center. Stijn Hoorens is head of the Brussels office of RAND Europe. Jonathan P. Caulkins is a former codirector of the RAND Drug Policy Research Center and is Stever Professor of Operations Research at Carnegie Mellon University.

Illicit drug use is a problem that spills across the wide-open borders of Europe. Considerable effort has been devoted to collecting information about the demand and supply of illegal drugs across the continent. Much of the work has focused on tracking demand-side indicators, such as problem drug use, demand for treatment, and drug-related deaths and infectious diseases.

Supply-side indicators are harder to define and thus to measure. Various law enforcement agencies report information on drug seizures, arrests, and prices, but in many European countries the current data-collection efforts are insufficient to gauge the effectiveness of supply-side interventions. For this reason, the European Commission asked RAND Europe to recommend ways to improve the understanding of illicit drug markets and supply-reduction efforts in Europe.

A Street Bag of Heroin Could Be Anywhere from Less Than 5-Percent Pure to More Than 95-Percent Pure

A Street Bag of Heroin Could Be Anywhere from Less Than 5-Percent Pure to More Than 95-Percent Pure

The foremost insight from our research is that it is crucial for European Union (EU) member states to collect information not just about raw drug prices but also about “purity-adjusted” prices. Heroin purity, for example, varies considerably across locations and time and is usually substantially less than 100 percent (see the figure). It would not be unusual if a gram of heroin purchased for €75 in one part of a city was 20 percent pure and in another place was 30 percent pure. The purity-adjusted prices would be €375 per pure gram in the first place (€75/0.2) and €250 per pure gram in the second (€75/0.3).

Since the drug distribution network could respond to law enforcement&endash;induced shortages by changing the amount of pure drug in each bag instead of changing the street price, a focus on the raw street price could lead to the incorrect conclusion that the enforcement effort did not influence the market.

For policy purposes, the utility of information about prices, arrests, and seizures depends not just on how much information is collected but also on how it is maintained in databases. Currently, most countries report information about the total number of drug seizures and the total weight to international organizations. However, this information is of limited value for understanding changes in drug markets and supply-side interventions, because it is not clear whether changes in seizures over time reflect strategic responses by drug traffickers, changes in law enforcement effort, or both.

Because some EU states are further along in developing data systems that can be used to measure the illicit drug supply, we offer recommendations for the immediate, near, and long terms. Recommendations for the immediate term do not require much coordination or large expenditures. Subsequent recommendations will likely require more of both.

Purities, Weights, and Users

The immediate need is for solid information about purity-adjusted prices. Fortunately, even some jurisdictions that do not make undercover purchases nevertheless analyze the purity of the illegal drugs that are frequently seized. Using just such forensic laboratory data on purity, we created a method to estimate purity-adjusted prices, combining self-reported price information with laboratory-provided purity information. This method requires only occasional (such as annual) observations of the nominal price per raw gram; these observations can be obtained from a variety of sources, including surveys of users.

Thus, the European Commission should obtain and analyze the purity information that is already available from forensic laboratories. Most of the respondents from a survey that we conducted of the European Network of Forensic Science Institutes reported that they do collect purity information in computer databases and would be willing to share it with researchers.

Also of immediate concern, the commission should help develop a formal network of researchers, law enforcement officials, forensic scientists, and policymakers to create a blueprint for building a pan-European database of drug seizures and to explore other ways that forensic laboratory data can be used. For example, we encountered a laboratory that had used chemical signature analysis, which is more detailed than typical purity analyses, to determine that all of the drugs originating in a single wholesale purchase had been distributed within just a few weeks. The laboratory was also able to use a separate analysis to link couriers arrested on different days by virtue of similarities in the design of the secret compartments in their luggage.

It is crucial to collect information not just about raw drug prices but also about “purity-adjusted” prices.

In the near term, we recommend that EU countries expand their reporting of drug seizures. Beyond information about the total number and total weight, it would be useful to know the median weight seized. That way, it would be possible to determine whether a few large seizures were having a disproportionate effect on the statistics. It would be preferable if this information were reported for “weight bins” (for example, seizures less than or equal to 1 gram, between 1 and 10 grams, between 10 and 200 grams, more than 200 grams). Such bins generally represent retail, mid-level retail, and wholesale transactions. Reporting the information by bins would allow law enforcement officials to learn whether certain activities were dominating the market.

In the long term, the commission could regularly collect information from heavy drug users, who account for most consumption and can therefore provide valuable information about prices, dealers, sales, and market conditions. It would also be helpful to obtain information about the typical quantity consumed by users, broken down by age, gender, race, ethnicity, and frequency of use. Other long-term goals include standardizing the definitions of drug-trafficking offenses and creating a pan-European database with consistent, incident-level information about drug seizures across Europe.

The purpose of creating better indicators and collecting additional information is to improve governments’ understanding of illicit drug markets and the effects of different supply-reduction efforts; such an understanding must underpin ongoing efforts to improve drug control strategies. The European Monitoring Center for Drugs and Drug Addiction’s efforts to develop consistent demand-side indicators have made it easier to follow consumption patterns, to make useful comparisons, and to target scarce prevention and treatment resources. Those efforts have taken years, and it would be surprising if it did not take time to develop indicators of similar quality on the supply side. Nonetheless, tangible benefits can be reaped in the short run with modest steps. square

Related Reading

Understanding Illicit Drug Markets, Supply-Reduction Efforts, and Drug-Related Crime in the European Union, Beau Kilmer, Stijn Hoorens (eds.), RAND/TR-755-EC, 2010, 223 pp. The other contributing authors were Jonathan P. Caulkins, Emma Disley, Priscillia Hunt, Susan Kirk, Rosalie Liccardo Pacula, Lila Rabinovich, Sudha S. Rajderkar, Jennifer Rubin, and Shruti Vasudev.