Crime prevention at one location often reduces crime at nearby untreated locations, because offenders overestimate the reach of the measure.
Clarke and Weisburd named the phenomenon in 1994 as the mirror image of displacement, and it is the better documented of the two. Offenders generally lack precise information about where a camera, patrol or lock scheme begins and ends, so uncertainty spreads the deterrent past its actual boundary.
In practice
- A camera on one entrance reduces theft at the unwatched entrance as well, for as long as nobody tests it.
- An audit of one department improves the paperwork of three that were not audited.