Problem-oriented policing often tries to reduce opportunities for crime. For example, window locks may be fitted to prevent burglary in an apartment complex, or closed circuit television cameras installed to prevent thefts in parking lots. These ways of reducing opportunities for crime often meet the same objection: all they do is move crime around, not prevent it. This theory of displacement sees crime as being shifted around in five main ways:

1. Crime is moved from one place to another (geographical).
2. Crime is moved from one time to another (temporal).
3. Crime is directed away from one target to another (target).
4. One method of committing crime replaces another (tactical).
5. One kind of crime is substituted for another (crime type).

In each case, the theory assumes that offenders are compelled to commit crime, whatever impediments they face. The basis for the assumption is either that the propensity to commit crime builds up and must be discharged in the same way that sexual release is sought, or that "professional" criminals or drug addicts must obtain a certain income from crime to maintain their lifestyles. There is no evidence that offenders must satiate some deep physiological appetite to commit crimes. In fact, there is plenty of evidence that people make choices about whether, where, and when to offend. Whatever its basis, the displacement assumption neglects the important role of temptation and opportunity in crime (Step 9).Even in the case of more committed offenders, the displacement theory fails to give enough importance to opportunity. Thus, research on drug addicts has shown that they adapt to variations in the supply of drugs. Nor is there any simple progression in drug use. Rather, addicts might be forced to use smaller amounts or less agreeable drugs because the supply of drugs has been cut.As for professional criminals like bank robbers, there is no reason to assume that they must obtain a fixed amount of money from crime. They would surely commit fewer robberies if these became difficult and risky, just as they would commit more robberies if these became easy. Bank robbers, like everyone else, may sometimes have to adjust to reduced circumstances and be content with lower levels of income.This does not mean that we can ignore displacement. Indeed, rational choice theory predicts that offenders will displace when the benefits for doing so outweigh the costs. For example, in the early 1990s the New York City Police deployed its Tactical Narcotics Teams to several high drug-dealing neighborhoods. Dealers responded by shifting their sales locations from curbside to inside the foyers of apartment buildings. But numerous other studies have found that displacement did not occur at all, or only to a limited extent. For example:

• Intensive gun patrols reduced firearms crimes in a Kansas City, Missouri high gun-crime neighborhood without displacing these or other crimes to nearby communities.
• New identification procedures greatly reduced check frauds in Sweden, with no evidence of displacement to a range of "conceivable" alternative crimes.
• Extensive target hardening undertaken in banks in Australia lowered robbery rates, but there was no sign that corner stores, gas stations, betting shops, motels, or people in the street began to experience more robberies.
• Burglary was not displaced to nearby apartment complexes when a problem-solving approach drove down burglary in a high-crime apartment complex in Newport News, Virginia.
• When streets were closed in the London neighborhood of Finsbury Park and policing was intensified, there was little evidence that prostitutes simply moved to other nearby locations. According to the researchers, many of the women working the streets in Finsbury Park were not deeply committed to prostitution, but saw it as a relatively easy way to make a living. When conditions changed so did their involvement and many seem to have given up "the game" (Step 50).
• Redesign of a trolley stop to curb robberies and assaults resulted in a reduction in violent crime at a San Diego, California location without shifting these crimes to other trolley stops.

In these examples and numerous others, the offenders' costs of displacing seemed to have outweighed the benefits and the examples bear out the argument that displacement occurs much less than commonly believed. This is the consensus of four different reviews of the displacement literature undertaken in the United Kingdom, Canada, the United States, and The Netherlands. The Dutch review (the most recent one) reports that in 22 of 55 studies from around the world in which displacement was examined, no evidence of it was found. In the remaining 33 studies, in which evidence of displacement was found, only some of the crime seems to have been displaced. In no case was the amount of crime displaced equal to the amount prevented. And in no case did displacement increase crime.Displacement is usually limited because offenders have difficulty adapting quickly. If they do make changes they are most likely to change to places, times, targets, methods, and crime types that are similar to those the prevention program blocks because these are the easiest changes for them to make. This suggests that displacement can be predicted by anticipating the easiest changes for offenders to make. If there are obvious easy changes, then you should consider how to incorporate these in your prevention plan. And if you cannot include them, then you should consider monitoring them to detect possible displacement.To sum up, displacement is always a threat, but there are strong theoretical reasons for believing that it is far from inevitable. In addition, the studies of displacement show that even when it does occur, it may be far from complete and that important net reductions in crime can be achieved by opportunity-reducing measures.