Does poverty cause violent crime?

An examination of the association between poverty and violent crime

Introduction

Poverty is associated with violent crime. As illustration, consider the association between county poverty rates and homicide rates in the United States. The correlation is fairly strong (r = 0.52) and highly statistically significant (p < 0.001).

The association between county poverty rate and its homicide rate is substantial. But why?

To look more closely at how the average homicide rate increases with poverty rate, we can split the counties into ten bins with roughly equal total populations. That is shown below.

Poverty rate decile (from least to most poor) and homicide rate.

The association is even clearer now. The 10% of people living in the poorest counties have almost 6 times higher homicide rate than the 10% living in the least poor counties. That poverty correlates with violent crime is not in dispute.

What is in dispute is whether that association is due to poverty causing violent crime. This is not merely a reflexive and baseless “correlation doesn’t imply causation” quip. There are good reasons—supported by strong empirical evidence—to seriously cast doubt on the causal potency of poverty on violent crime.

There are many odd facts in need of explanation if one is to believe that economic conditions have a great causal impact on violent crime. Why do NFL players, with average salaries in the millions of dollars, not have lower violent crime arrest rates than the general population (Leal et al., 2015)? And why did the homicide rate fall during the Great Depression, one of the most severe economic crises? The answer, it turns out, is that poverty and violence are correlated for other reasons.

There are three (not mutually exclusive) potential explanations for the poverty-violence association:

1. Causal: poverty affects propensity for violence.

2. Reverse causal: crime harms economic conditions.

3. Selection/confounding: other variables affect both economic prospects and propensity for violence.

As I will argue, the causal effect of poverty on violence is weak, and potentially practically null. Instead, the association between poverty and violent crime is mostly the product of selection: traits like low cognitive ability, mental disorders and others, negatively impact economic success and are also risk factors for committing violent crime.

I will first review some evidence regarding reverse causality and selection, and establish their important role in the poverty-violence association. Afterwards, I will review a broad body of causally informative evidence and evaluate to what extent poverty affects violent crime.