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Illegal Drug Markets in Portland, Oregon

Illegal Drug Markets in Portland, Oregon

Northeastern University

Synopsis: The ease of customer accessibility outweighs the effect of possible sanctions in the presence and location of outdoor illegal drug markets.


Community Need

By understanding the factors that drive illegal drug market locations, police can better focus their resources to reduce crime. This study aims to identify the key geographic factors that explain the locations of illegal drug markets. In order to exclude drug offenders from sensitive areas where drug dealing was common in the past, “drug free zones” have been implemented as a strategy that fights crime through a geographic lens. This study also examines the efficacy of drug free zones in Portland from 1990-1998.


From 1992-1997, Portland introduced four drug free zones. Anyone arrested for a drug offense was excluded from any drug free zone for 90 days and, if convicted, was excluded from all drug free zones for one year. The only exceptions were if the person lives, works, or attends school in a drug free zone. If the police find a person who has been convicted of a drug offense in a drug free zone, they arrest them on a trespassing charge. Police were dispatched to drug free zones to target known drug offenders.


Primary Research Question(S)

The current study explores two questions:

  1. Are customer location and accessibility to illegal drug markets related to drug sale arrests?
  2. Do increased sanctions associated with drug free zones effective in decreasing drug sales arrests?

Research Design

Growth curve modeling was used to explore changes in patterns of drug sales arrests. Researchers used Portland drug sale arrest data from 1990-1998. The researchers looked at the following variables to predict a block group’s propensity for drug sale arrests: how far away the block group was from the central business district (CBD), whether the block group was located in the northeast police precinct after the implementation of the downtown and eastside drug free zones, the number of bus stops in the block group, and the centroid longitude of the block group.


To measure the effects of drug free zones, for each year from 1990-1998 the researchers used a “yes/no” variable to represent whether a block group was in a drug free zone each year. However, it was likely these block groups were already under increased scrutiny before being designated as drug free zones. Researcher also did not study the effect of having visible drug free zone signage in businesses and stores. Lastly, the arrest data in the study represents visible drug markets that the police were able to intercept and does not account for “indoor” drug markets.


Research Findings

Researchers found the following geographic explanations for arrest propensity: a block group’s arrest propensity increased the closer it was to a Central Business District, increased if it was located in the northeast precinct in Portland, increased with higher number of bus stops, and increased the further east it was relative to other block groups.

A block group’s population size had a significant positive relationship with the number of drug sales arrests. For each additional person (potential customer) in an area, the number of drug sale arrests increases by a factor of 1 while controlling for all other variables in the model. As the average number of police officers increases in a block group, the number of drug sales arrests increases by a factor of 1.07.

With all other explanations of drug sales arrests controlled for, the study showed that whether a block group is contained within a drug free zone is not a significant predictor of changes in drug sale arrests.

Main Implications

This study found that the location of illegal drug markets are driven by accessibility to their customers (such as a central business district with strong public transportation). The study also found that regarding drug free zones, increased sanctions for those arrested and convicted with drug offenses does not lower the number of drug sale arrests. The profitability of sought-after locations that are accessible to customers of the illegal drug market outweigh the threat of increased sanctions for drug offenders. Additionally, researchers found that there were many similarly desirable locations for offenders to set-up drug markets that were located very close to drug free zones.


Robinson, J. B., & Rengert, G. F. (2006). Illegal drug markets: The geographic perspective and crime propensity. Western Criminology Review, 7(1), 20-32.