Violent power laws

From The 1 % of the population accountable for 63 % of all violent crime convictions by Örjan Falk, Märta Wallinius, Sebastian Lundström, Thomas Frisell, Henrik Anckarsäter & Nóra Kerekes.  From the Abstract:

Purpose

Population-based studies on violent crime and background factors may provide an understanding of the relationships between susceptibility factors and crime. We aimed to determine the distribution of violent crime convictions in the Swedish population 1973–2004 and to identify criminal, academic, parental, and psychiatric risk factors for persistence in violent crime.

Method

The nationwide multi-generation register was used with many other linked nationwide registers to select participants. All individuals born in 1958–1980 (2,393,765 individuals) were included. Persistent violent offenders (those with a lifetime history of three or more violent crime convictions) were compared with individuals having one or two such convictions, and to matched non-offenders. Independent variables were gender, age of first conviction for a violent crime, nonviolent crime convictions, and diagnoses for major mental disorders, personality disorders, and substance use disorders.

Results

A total of 93,642 individuals (3.9 %) had at least one violent conviction. The distribution of convictions was highly skewed; 24,342 persistent violent offenders (1.0 % of the total population) accounted for 63.2 % of all convictions. Persistence in violence was associated with male sex (OR 2.5), personality disorder (OR 2.3), violent crime conviction before age 19 (OR 2.0), drug-related offenses (OR 1.9), nonviolent criminality (OR 1.9), substance use disorder (OR 1.9), and major mental disorder (OR 1.3).

Conclusions

The majority of violent crimes are perpetrated by a small number of persistent violent offenders, typically males, characterized by early onset of violent criminality, substance abuse, personality disorders, and nonviolent criminality.

Most the Scandinavian countries are both very centralized and their government systems are very integrated with one another.  It allows them to do research with a degree of rigor and accuracy which could never be accomplished in our decentralized governance and data systems which prioritize individual privacy over the alternate approaches.  It is nice to have the Scandinavia data but I prefer our governance system.

It is not surprising to find a power law (Pareto distribution) in criminal activity.  All human biological and social systems tend to demonstrate power law distributions.

What is astonishing here us just how concentrated it is.  1.0% of criminals are responsible for 63% of all violent crimes.  And, as is found in all countries, violent crime is primarily a male outcome.  We are usually starkly avoidant of empirically based stereotypes, but male violence is, for whatever reason, the stereotype with which all are comfortable.

Do these Swedish findings translate to the US?  Almost certainly but with great nuance.  We have far more diversity of race, ethnicity, religion, class, education, income, labor force participation rate, etc. than does Sweden.  Which is what makes the whole field extremely delicate.  

But a first order of magnitude crude estimation provides affirming confirmation.  African American males between 15 and 35 are responsible for some 50% of all murders in the US.  And they are dramatically concentrated in cities.  Very, very crudely, that is probably 3% of the population responsible for 50% of murders.  Not as bad as Sweden's 1% and 63% but certainly in the ballpark.

Sweden is more heterogenous than it was when I lived there in the early seventies.  It would be interesting if their research allowed for any sort of distinction between native born versus immigrant for example.

Regardless, this research provides a very powerful confirmation of the power law when it comes to violent crime.

Another study, this one just out, emphasizes the Pareto distribution of crime by geography.  From Crime Hot Spots: A Study of New York City Streets in 2010, 2015, and 2020 by David Weisburd andTaryn Zastrow.

Recent data in New York City suggest that violent crime is on the rise. However, over the last three decades, there has been a more than 70% decline in index crimes as reported by the FBI. This led to a growing perception, especially among critics of policing, that crime in NYC had become a marginal problem, or at least that it had declined to levels such that there was no need to place too much emphasis on crime control. Combined with concerns about police abuses and claims of disparities in policing in minority and disadvantaged communities, this fueled calls for defunding the police.

In this report, we focus on the high-crime hot spots where 25% and 50% of NYC crimes were committed. The crime numbers on those streets suggest that, despite the encouraging overall crime decline over the past few decades, many city streets continue to have very high crime levels that need to be addressed by police and other agents of the city government.

Our report looks beyond general crime statistics to the hot spots of crime where much crime in a city is concentrated. Looking at NYPD crime reports for 2010, 2015, and 2020, we find that about 1% of streets in NYC produce about 25% of crime, and about 5% of streets produce about 50% of crime. This is consistent across the three years, showing that a very small proportion of streets in the city are responsible for a significant proportion of the crime problem.

Mapping crime in NYC, we found that high-crime streets are spread throughout the city, though concentrated in Manhattan, the Bronx, and Brooklyn. In turn, we observed a good deal of street-by-street variability, with the highest-crime streets often adjacent to streets with little or no crime. This means that it is misleading to classify whole neighborhoods as crime hot spots, since the majority of streets—even in higher-crime areas—are not. This is an important lesson for police and ordinary citizens who mistakenly see very large areas as crime-ridden. We also found a good deal of stability in the locations of crime hot spots. Nearly all the streets that were hot spots as we have defined them in 2010 were also hot spots in 2020. 

Graphically, 10% of streets are responsible for 75% of violent crime in New York City.  

And third, for violent crimes, just 10% were responsible for 75% of them. pic.twitter.com/wl8X7y4yZp

— Crémieux (@cremieuxrecueil) April 16, 2023

 A very small percentage of citizens commit the great majority of violent crime and those violent crimes are extremely concentrated in just a small part of cities.