What do the statistics tell us about homicides and why they happen?

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The recently issued Milwaukee Homicide Review Commission’s 2015 Annual Report on Homicides and Non-Fatal Shootings contains a wealth of information on where homicides occur and who are the victims and perpetrators. For starters, homicides and non-fatal shootings are heavily concentrated in certain neighborhoods. The following map, taken from the report, shows the firearm incident density—homicides and non-fatal shootings superimposed on a map of poverty.

The report can help give an idea of who the victims are. First, they are far more likely to be male than female, as shown in the next graph, showing homicides and nonfatal shootings in 2015. (The Journal-Sentinel publishes an on-going database of homicides. So far, the profile of victims and suspects for 2016 looks a lot like that for 2015.)

The next graph shows the relationship of age to the likelihood of being a victim (either fatal or nonfatal) of a shooting. It shows the relationship of the age of the victim and the number of homicides (in gray), of non-fatal shootings (in blue), and total shootings (in red).

The report divides the victims by age ranges. For example, 200 victims of shootings (both fatal and nonfatal) were between age 20 and 24, or an average of 40 per year for each of the five years in this range. Thus I plotted 40 at the range’s midpoint, 22.5 years. The most vulnerable period falls between the late teens and late twenties.

The chance of being a victim also varies widely with ethnicity. The next graph shows the rate per 100,000 of being murdered or suffering a nonfatal shooting.

Put these factors together and Milwaukee’s most vulnerable residents are young black males from their late teens to late twenties. The report calculates that between age 15 and 24 they suffer a homicide rate of 187 per 100,000 and a nonfatal shooting rate of 1,109. Put another way, they have well over a 1 percent chance of being shot during every one of those ten years.

Lacking all those factors, the chances of being shot go way down even if one lives in the same dangerous neighborhood. The tragedy of nine-year-old Za’layia Jenkins, who was shot and died while watching television, gained so much attention in part because her case was so unusual. She did not fit the profile of most victims but was caught in the cross-fire.

Who are the perpetrators of the homicides and nonfatal shootings? A plot of suspects shows a similar pattern. As with victims, the numbers rise rapidly in the late teens, peaking in the twenties, and falling thereafter.

The next chart of this series compares victims and suspects. The gap between victims and suspects reflects Milwaukee’s clearance rate of 60 percent which, while better than the national average, means about 40 percent of perpetrators are not identified.

Like their victims, the suspects are likely to be male and black. This is consistent with the next finding, that suspects and victims are likely to have known each other. As the next graph shows, around 70 percent know each other, either as acquaintances or family members.

These and other findings listed in the report are reflected in Milwaukee Police Chief Edward Flynn’s list of four risk factors:

Don’t be part of a crime gang or crew

Don’t be a drug dealer

Don’t illegally carry a gun

And finally, “If you are in an argument with a stranger, ask them how often they’ve been arrested. If they’ve been arrested more often than you’ve been arrested, concede the point.”

Although Flynn’s list was criticized by members of the Common Council, it is good advice. A young man following those rules vastly reduces his chances of being shot. As the case of Za’layia Jenkins shows, those who ignore this advice make their neighborhoods more dangerous and are a threat to people who are just minding their own business.

The next chart shows the five largest causes of shootings, both fatal and nonfatal. To some extent, the categories are arbitrary, but they (and others not shown) seem to fall into one of two broad categories:

Crimes of the moment, such as an argument or the urge to revenge a slight.

Shootings committed as part of a crime such as robbery or drug dealing.

The first cause is much more likely to lead to death than the second. This fits in with Flynn’s last point. The majority of suspects already have a criminal record. Although the proportion is smaller, the same is true of the victims.

Only eight of the suspects identified in 2015 shootings had no criminal history. In part this might reflect the fact it is harder for the police to identify suspects not already in their files. With that caveat, this result supports Flynn’s last point. 38 percent of shootings by suspects with criminal records result in death, compared to 13 percent of those by people with no prior record.

The report devotes a single page to four strategies aimed at reducing the homicide rate in Milwaukee. These are in various stages of development and it is not clear at this point how effective they will be.

In Milwaukee, guns—mostly handguns—were the weapon of choice in homicides, as can be seen in the next chart showing the kind of weapon used in last year’s homicides. Would a program to reduce the availability of guns be effective in reducing Milwaukee’s homicide rate?

Most studies show a strong correlation between the availability of guns and homicides. Some of these studies were summarized in a previous Data Wonk article.

A recent article in Slate surveys research on the question of whether having a gun makes one safer.

A study published in 2014 in the journal Injury Prevention examined the relationship between the prevalence of guns and homicide rates in the USA and “found that state-level gun ownership … is significantly associated with firearm and total homicides but not with non-firearm homicides.”

examined the relationship between the prevalence of guns and homicide rates in the USA and “found that state-level gun ownership … is significantly associated with firearm and total homicides but not with non-firearm homicides.” A 2013 study analyzed the relationship between gun ownership rates in developed countries and gun deaths. It summarized its findings as follows: “The number of guns per capita per country was a strong and independent predictor of firearm-related death in a given country, whereas the predictive power of the mental illness burden was of borderline significance in a multivariable model. Regardless of exact cause and effect, however, the current study debunks the widely quoted hypothesis that guns make a nation safer.”

A 2004 study published in the American Journal of Epidemiology found “that regardless of storage practice, type of gun, or number of firearms in the home, having a gun in the home was associated with an increased risk of firearm homicide and firearm suicide in the home.”

Although the Milwaukee Homicide Review Commission report does not attempt to estimate the gun density for differing neighborhoods, it seems likely that the myth that guns make one safer acts to make these neighborhoods more dangerous. Both Milwaukee and its neighbor Chicago have suffered a recent surge of gun violence. Both cities are surrounded by jurisdictions where it is easy to buy a gun.

Organizations like the National Rifle Association likely contributed to the surge in gun deaths in several ways, such as fighting measures to reduce the availability of guns, by spreading the myth that having a gun makes one safer, and by discouraging research on the connection between the availability of guns and gun homicides.

In Milwaukee, the violence is concentrated in a small geographic area, one with a high rate of poverty, a high unemployment rate, and a dearth of jobs. This area, as with similarly impoverished areas in other cities, suffers a vicious cycle: high crime drives away potential employers while the lack of jobs contributes to crime. Any effective strategy to reduce the violence would have to include increased availability of public service jobs, given the difficulty of attracting private sector employers.

Rather than scapegoating the police for the spike in homicides, Milwaukee needs to extend the research to discover strategies that work.