California’s overall crime rates are down, but numbers don’t reveal the whole story

In a previous post, we announced that California Attorney General Rob Bonta has officially released state crime data for 2021. He eagerly noted that violent and property crime rates are well below the historic highs seen in the mid-1990s, but whistled past the fact that violent crime rates have been slowly climbing since the early 2000s. The contradictory shifts in violent crime versus property crime are somewhat perplexing. While overall crime rates might be down, violent crimes, particularly aggravated assaults and homicides, have been increasing.

Looking at the numbers all together, it is important to keep in mind: all crimes are not created equal in the harm they cause. For example, homicides are a relatively rare event, yet they are much more harmful than high-frequency crimes like larceny. For example, an increase of 500 thefts would be a small change in the overall number of thefts and would have little overall impact on public safety, whereas an increase of 500 homicides would be a large change in the overall number of homicides and have a very detrimental impact on public safety. By looking at crime statistics though, these nuances can be overshadowed.

Figure 1. Property Crime Rates

Taking a deeper dive into the data shows some of these nuances a little better. Figure 1 shows that overall property crime has indeed been declining steadily since 1985, but it also shows how much variation there is in different property crime rates. The overall decline is driven by decreases in larceny though, arguably the least harmful crime out of them all. Burglary rates have also been trending downward, but the decline is much less dramatic. In contrast, motor vehicle theft has been on an upward trend since 2008.

Figure 2. Violent Crime Rates

Looking at violent crime rates tells a different story (see Figure 2). Despite remaining lower than the historical highs seen in the mid-1990s, it is hard to ignore the fact that violent crime has been trending upward since the early 2000s, and current rates mirror those seen in the early 1990s. The changes in violent crime are driven largely by aggravated assaults, though homicides are also on the rise. But these shifts in violent crime are obscured by the massive decline in property crimes that has driven the overall crime rate downward.

Just because the overall crime rate is down does not mean that our cities are safer, mostly because different crimes vary in the amount of harm they cause. For example, aggravated assaults, the most common violent crime, often involve a deadly weapon and typically result in serious bodily injuries. Thus, aggravated assaults are often a sliver away from becoming attempted murder or murder. Further, perpetrators with histories of aggravated assaults are more likely to eventually commit murder in the future. Additionally, some scholars have pointed out that Americans might face a greater risk of crime while in public despite the decreases in overall crime.

Figure 3. Homicide Rates

Homicides are hard to see on the above graph due to their low rates relative to other crimes, yet they deserve a closer look. As shown in Figure 3, homicides are a rare event, yet are undoubtedly the most harmful out of all crimes. Homicides declined between 1985 and 2000, but since then, rates have been inconsistent. There were major peaks in homicides in 2003 and 2006, followed by a major drop in 2008. Since 2008, homicides have been steadily increasing. This increase became even more substantial in the last few years, with the largest single-year increase in state history occurring from 2019 to 2020 (+31%).

Looking at the above graphs, it’s easy to see why we should distinguish between different types of crime. The rise in violent crime, especially homicide, is particularly worrisome. Fewer people are directly affected by aggravated assaults and homicides though, so it can be hard to fully understand the amount of harm caused to the victims (and their families) who do experience them. When violent crimes goes up, life goes on as normal for many of us, but these crimes are life-changing for victims and their families. Murder victims are deprived of their basic human right to life, while their family members will suffer enormous grief for years to come. Victims of aggravated assaults often experience severe psychological trauma that can take years to work through. Many victims of assault also incur permanent injuries that affect them for the rest of their lives — sometimes ruining their ability to work or engage in their favorite hobbies. The harm caused by these crimes needs to be acknowledged, and downplaying this fact with the statement that “overall crime is decreasing” is negligent at best and abhorrent at worst.

Crime Harm Indicies: A New Way of Looking at Crime

The above data reflect the simple and most common method of measuring crime — counting the number of crimes and calculating the rates per 100,000 people. But because not all crimes are created equal, therse numbers aren’t the best for understanding the impact on public safety. As an alternative strategy to looking at crime and public safety, leading criminologists have developed a “crime harm index,” which measures how harmful different crimes are in proportion to others. This approach weights offenses based on how much harm they cause, with larger weight given to more harmful crimes (e.g., murder, aggravated assault).

Developed by renowned researchers Lawrence W. Sherman, Peter Neyroud, and Eleanor Neyroud, the approach was piloted in Cambridge, England in 2016 and appropriately named the “Cambridge Crime Harm Index.” The harm scores for each crime are based on the sentencing guidelines of England and Wales. For serious crimes, the harm score is equivalent to the default prison sentence that an offender would receive for committing it, if committed by a single offender with no prior convictions. For minor offenses that are punishable by fines, the harm score is equivalent to the number of days it would take someone with a minimum wage job to earn the money to pay the fine. Since 2016, the approach has been adopted by several UK police forces, and has also inpsired other crime harm indicies for New Zealand, Denmark, Western Australia, and Canada. The index was most recently updated in 2020 and is publically available.

By using a single sum of weighted crime harm across all crime types, the crime harm indicies are much more reliable indicators of public safety. From a research standpoint, use of a harm index adds additional context to the usual measures of success or failure and can help clear up some of the confusion around crime statistics. For example, a crime hot spot might see improvements in levels of general social disorder and low-level crimes, but this does not necessarily mean that violent crimes in the area are declining. Thus, it could lead to a false belief that the community is safer. Including a crime harm metric helps untangle some of this confusion and provides a better idea of actual public safety risk.

From a practical standpoint, this approach considers crime harm and crime count to guide decision-making, helping immensely in targeting the highest-harm places and the most harmful offenders, while prioritizing services for the most harmed victims. This delineates a clear focus on cutting the harm from crime rather than just cutting down on the volume of low-harm crimes. This also helps manage demand for limited police services and victim resources. More serious crimes require more resources to prosecute and convict the most dangerous offenders, and including a crime harm metric helps police deploy resources to hot spots based on need and type of concern.

Conclusion

The key takeaway is that “crime” and “violence” are two different things. Just because overall crime rates are down does not mean that our communities are safer. Distinguishing different crimes based on the harm the cause  is a necessary to formulate policies that actually make our communities safer. But of course, politicians don’t make these distinctions, and unfortunately it is not in their best interest to do so.