Defining Displacement

Crime displacement is the relocation of crime from one place, time, target, offense, or tactic to another as a result of some crime prevention initiative. Spatial displacement is by far the most commonly recognized form,1 though the other four are also frequently acknowledged by those studying crime prevention effects. Formally, the possible forms of displacement are:2†

† Also sometimes listed is offender displacement (when new offenders take the place of offenders who were arrested or have desisted from crime), but this is actually offender replacement. Displacement is a term reserved for changes offenders make so they can continue to offend when faced with reduced opportunities.

• Temporal – offenders change the time at which they commit crime;
• Spatial – offenders switch from targets in one location to targets in another location;
• Target – offenders change from one type of target to another;
• Tactical – offenders alter the methods used to carry out crime; and
• Offense – offenders switch from one form of crime to another.

Overall, displacement is viewed as a negative consequence of crime prevention efforts, but in some cases it can still provide some benefit. Current thinking on crime displacement suggests that beneficial or "benign" displacement can occur when the harm produced by the displaced crime or problem behavior is less than what existed before the intervention.3 Specifically, benign displacement can occur in a variety of ways and is when the displaced crime is:

• Less serious, such as the shift to petty thefts from robbery
• Less impactful on the community, which can occur three ways:
  1. The concentration of crime is redistributed across a larger pool of victims (i.e., relocating victimization from a small group of repeat victims).††
  2. The crime is transferred away from more vulnerable groups of the population, such as children and the elderly.
  3. The crime is relocated to places where the community impact is less harmful. For example, a street drug or prostitution market relocates from a residential area to a remote area, which would reduce fear of crime or residential and business decay, or the same volume of crime disperses to a larger area where the harm is less concentrated.
• Lower in volume. For instance, the target area may experience a reduction of 100 crimes post response, but the displacement of the crime resulted in an increase of 50 crimes in the comparison area post response. Thus, a net reduction of 50 crimes was achieved.

†† For more on repeat victimization, see the Problem-Oriented Guides for Police Problem-Solving Tools Series No. 4 entitled, Analyzing Repeat Victimization.

At worst, displacement can lead to more harmful consequences. This occurs when there is a shift to more serious offenses or to similar offenses that have more serious consequences.4 Referred to as "malign" displacement, it involves any situation where the relocation of crime makes matters worse. This could be an increase in the volume of crime at the relocated area, a shift to more serious crime types, the concentration of crime to a smaller group of victims, the relocation of crime to places where it has greater impact on the community, or the relocation of crime to more vulnerable groups of the population.

Diffusion of Crime Control Benefits

The opposite of crime displacement is diffusion of crime control benefits. Crime diffusion entails the reduction of crime (or other improvements) in areas or ways that are related to the targeted crime prevention efforts, but not targeted by the response itself.5 Though less recognized than displacement, diffusion is recorded in many research evaluations of crime prevention responses.6 Diffusion effects are referred to in a variety of ways including the "bonus effect," the "halo effect," the "free-rider effect," and the "multiplier effect." In cases where any degree of diffusion is observed, the benefit of any response effects experienced in the targeted area are amplified as improvements were gained without expending resources in those areas.

As with displacement, diffusion of benefits can occur in many forms. Spatial and target diffusion occurs when areas or other crime targets near the intervention zone also experience a reduction in crime. Temporal diffusion occurs when other time periods experience a reduction in crime even though the intervention was not applied during those times. Crime type diffusion occurs when other crime types are prevented even though they were not targeted by the intervention (for instance, a project targeting commercial burglary may also achieve an added reduction in shoplifting).