Analyzing violent crime—Analytics

Broken Bottles

Despite an overall decline in crime, the bloodshed and violence continues in many of the City's poorest neighborhoods. Frustrated and distressed, community and religious leaders are calling for immediate action. Citing studies linking alcohol to gang violence and to other violent crime, they are putting pressure on city and state officials to close liquor establishments, to decline new liquor license requests, and to reduce access to alcohol in the most violent neighborhoods. Meanwhile, local business owners are banding together, rallying to block the proposed restrictions. They cite violations of the fifth and fourteenth U.S. Constitutional Amendments and claim the proposed restrictions would negatively impact the social fabric and tourism of the City.

The Chief of Police is asking you, the Crime Analyst, to determine if there is indeed a relationship between violent crime and liquor establishments in your City. She wants your recommendations for an effective solution.

You know that this issue has surfaced for different cities around the country and that a number of research studies have demonstrated a correlation between liquor establishments and violent crime. There are also theoretical explanations supporting this relationship such as routine activity theory and social disorganization theory.

Your workflow is summarized below.

What data will you need?

Since you are interested in violent crime, you collect data for the homicides, rape, robbery, aggravated assault, and aggravated battery incidents over the past year. Next, using ArcGIS Business Analyst, you obtain a dataset of businesses that either sell or serve alcohol (this includes bars, nightclubs, lounges, taverns, liquor stores, and so on). If you need additional data, you will use the data enrichment tools in ArcGIS to get it. Your point data is shown below.

Liquor vendors in blue; Violent crime incidents in brown — It is difficult to discern spatial patterns with so many points on the map.

Where are the violent crime hot spots? Where are the hot spots for businesses selling or serving alcohol? Do they overlap?

To make sense of the more than 22,000 crime points, and over 1,500 business points, you map them using hot spot analysis. These maps show you the statistically significant hot spots (red) and cold spots (blue) for violent crime and for liquor establishments. If violent crime is linked to liquor establishments, you expect to see spatial correspondence between their activity spaces.

Compare the violent crime and liquor vendor hot spot maps — The violent crime and liquor vendor hot spot maps look very different.

You notice some overlap in the downtown area. To ensure that the remediation efforts you propose focus on your city's most vulnerable neighborhoods, while avoiding areas that could impact tourism, you will need a better understanding of neighborhood poverty patterns within those overlap areas.

Where are the City's most vulnerable neighborhoods?

You obtain the data needed to create a hot spot map of poverty.

Poverty hot spots — The red areas are statistically significant hot spots for poverty.

Which areas should be included in a moratorium on new liquor licenses?

You will recommend remediation measures for statistically significant hot spots (99 percent confidence) across all three variables: violent crime, existing liquor establishments, and poverty. To find these areas, you overlay all three maps, keeping only the hot spot locations that overlap.

With the exception of the small overlapping areas identified above, you didn't find a strong spatial correlation between violent crime and businesses that sell or serve alcohol.

Still, the community representatives have indicated that the problem is serious. While you work with numbers every day, you know that there are real faces—real people—behind your data. You decide to dig deeper.

Has violent crime been increasing in the City? If so, where?

Space-time pattern mining will show you if violent crime has been increasing or not. The maps below show the results of this analysis. You notice several locations with intensifying violent crime hot spots and a number of persistent hot spots as well. Consecutive hot spots are also worrisome; these represent hot spot locations that have been statistically significant for several of the most recent time periods.

Violent Crime Trends — There are several concerning trends including new, intensifying, and persistent hot spot areas.

The 3D map below is zoomed in to the area of both sporadic and consecutive violent crime hot spot trends in the downtown area. The green squares at the base of the map delineate one of the liquor moratorium remediation areas you identified above. Each bin in the 3D stack represents a four-week time period, with the most recent time period at the top. The darkest red bins reflect locations and time periods with intense violent crime activity.

A 3D view of violent crime trends downtown

There are definitely locations around the City where violent crime is persistent and even intensifying; most of these do not correspond to high densities of businesses serving or selling alcohol, however.

What else might be contributing to violent crime?

Two years ago the City implemented a Summer Jobs Program that has proven tremendously effective at reducing violent crime. You obtain unemployment data and repeat your hot spot analysis to see if you find a stronger spatial correlation between unemployment and violent crime than you did between liquor establishments and violent crime. Interestingly, you do.

Compare the violent crime and unemployment hot spot maps — There are a number of locations where the violent crime and unemployment hot spots overlap.

Where do persistent, intensifying, and consecutive hot spots overlap with unemployment hot spots?

You will recommend remediation measures for the areas where persistent, intensifying, and consecutive hot spot trends overlap with the statistically significant unemployment hot spots (99 percent confidence).

Overlap between violent crime trends and unemployment hot spots — The blue areas are the locations where intensifying, persistent, and consecutive hot spot trends overlap with the most intense unemployment hot spots.

Which specific high schools should be targeted for an expanded summer jobs program?

You identify high schools within a quarter mile of the remediation areas where high violent crime and high unemployment overlap.

Selected schools — You will recommend that several schools be included in an expanded summer jobs program.

Your analyses have gone well! You have several recommendations to propose to the Chief of Police.

Final recommendations

Your final report will include the map above showing your recommendations below.


	Areas with high densities of violent crime, businesses selling or serving alcohol, and poverty. Suggested remediation: Review the existing liquor licenses for violations. Impose a moratorium on new liquor licenses.
	Areas with intensifying or persistent violent crime and high unemployment rates. Suggested remediation: Add the public high schools within 0.25 miles of these areas to the existing summer jobs program. Consider a PR campaign to make people aware of the tremendous success this program has had on reducing violent crime over the past two years.
	New violent crime hot spots. Suggested remediation: Assign additional officers to these areas in order to assess root causes and to identify strategies that might keep violent crime in these areas from becoming endemic.
In addition, it will be important to evaluate the space-time violent crime patterns monthly to assess the effectiveness of these remediation measures.