Because bank robbery is not a common crime, it may appear random, which suggests that all banks are at a high risk of robbery. In the short-term, however, the vast majority of branches do not get robbed. As an example over a 1 year period 14 percent of branches in Philadelphia, Pennsylvania were robbed.
As the time period increases, however, more branches are victimized: in two years, 31 percent of branches in Washington, D.C. were robbed; in five years, percent of branches in California were robbed; and in 10 years, 52 percent of branches in Washington, D.C. were robbed.
The increasing percentage of robbed branches levels off over time: after 10 years, nearly half of all bank branches will not have been robbed, while branches that have been robbed once are often robbed again—a phenomenon known as repeat victimization.
Because robbed branches are often robbed again, these contribute disproportionately to the number of bank robberies.
- In Seattle, Washington, 63 percent of robbed branches were victimized two or more times; these generated 82 percent of all robberies during a four and one-half year period.
- In Washington, D.C., 12 percent of branches were robbed five or more times in 10 years; these branches generated more than one-third of all bank robberies during this period.
- Robbed branches are distinctly different from unrobbed branches in their future victimization risk. A branch that has never been robbed faces a low risk of robbery, whereas a robbed branch has a substantially higher risk. In Indiana, for example, robbed branches were three times more likely to be robbed in the succeeding three years than unrobbed branches. A branch that has been robbed multiple times faces the highest risk of all.
- Repeat robberies may be committed by a robber who returns to reprise a successful crime or to complete an attempted crime. A repeat robbery is particularly likely if the robber felt the crime was easy; many offenders describe bank robberies this way.
- The pattern of repeat victimization is so strong that not all repeat robberies can be attributed to repeat offenders. Repeat robberies also occur because the features that attracted an initial robber—such as an easy escape route that remains unchanged—are likely to attract other like-minded robbers. Some believe that publicity about successful bank robberies attracts copycats, but there is no evidence that this is so.
- Studies show that the risk of repeat victimization is most acute in the short-term: at least one-third of repeat bank robberies occur within two months of a previous offense. Because bank robberies are a low volume crime, multi-year data is often necessary to identify such patterns. Repeat victimization continues over longer periods of time; these patterns can best be identified when robbed and unrobbed banks are compared. The risk of repeat victimization is so strong that robbed banks are often surrounded by unrobbed banks.