Step 18: Learn if the 80-20 rule applies
- Repeat Offenders In Wolfgang's famous Philadelphia cohort, about 5 percent of all offenders in the study were responsible for more than 50 percent of the crimes.
- Repeat Victims According to the British Crime Survey, repeat victims (just over 4 percent of all victims) endure 40 percent of the crimes reported in the survey (see Step 29).
- Hot Spots In the landmark paper that put this concept on the map, so to speak, Lawrence Sherman and colleagues found that 6 percent of the addresses in Minneapolis accounted for 60 percent of the calls for police service.
- Hot products Annual data produced by the Highway Loss Data Institute show that theft claims for some automobile models are as much as 30 times greater than for other cars (see Step 31).
- Risky Facilities In Danvers, Massachusetts, 3 out of 78 stores (5 percent) accounted for 55 percent of shoplifting incidents reported to the police (see Step 28).
- Make a list of the people, places, or products, with a count of the number of events associated with each of these.
- Rank order them according to the number of eventsassociated with each - most to least.
- Calculate the percentages of the events each person, place, or product contributes. In the table, there are 386 incidents of theft and burglary. Sixty of these incidents (15.5 percent) occurred at construction sites owned by Builder 1.
- Cumulate the percentages of incidents starting with the most involved person, place or product (or in this example, home builders).
- Cumulate the percentages of the people, places, or products (in our example, the cumulative percentage of home builders in column 5).
- Compare the cumulative percentages of people, places, or products (column 5) to the cumulative percentage of outcomes (column 4). This shows how much the most involved people or places contribute to the problem.
At the analysis stage, these kinds of tables can help in determining if there are important differences among people, places, or products at the top and those at the bottom of the list. In our example, Stacy Belledin found that an approximate measure of the numbers of homes built correlated fairly well with the numbers of thefts and burglaries experienced by each builder, but it did not explain all the differences in risk. Other possibly important sources of these differences could be the neighborhoods where builders were operating, their police reporting practices and their standard security precautions.
Reported Thefts and Burglaries at Construction Sites 55 Home Builders, Jacksonville, FL , Jan. - Sept 2004
Percentage Of Incidents
Cumulative Percentage Of Incidents
Cumulative Percentage Of Builders
|3 Builders, 4 Incidents||12||3.0%||94.8%||32.7%|
|3 Builders, 3 Incidents||9||2.4%||97.2%||38.2%|
|1 Builders, 2 Incidents||2||0.5%||97.7%||40.0%|
|9 Builders, 1 Incident||9||2.3%||100.0||56.4%|
|24 Builders, 0 Incidents||0||0.0%||100.0||100.00|