In his analysis of crime patterns over the period of 1990-2006, Douglas Clement examined mountains of data on crime rates and other variables from 289 counties in the US, seeking to clarify their interrelationhips over time and across counties.
Here’s what Clement found:
Income and population: One would think that per capita income would have a strong positive link to crime, other variables held constant. But when population was also included in in the data analysis, income lost its statistical significance, while population remained significant, suggesting that highly populated counties will have higher crime rates, regardless of their income levels.
Unemployment: higher unemployment rates were associated with higher crime rates in district counties, but the quantitative importance of this variable and statistical significance was very small, meaning that changes in unemployment didn’t have much explanatory power. This finding is consistent with what most other empirical studies have found.
Police officers: The number of police officers had little or no statistical relationship to crime rates when other variables were taken into account.
Clearance rates: Calculated as a ratio of the number of arrests to the number of offenses, clearance rates were strongly associated with crime, in a negative direction, meaning that higher rates of arrests-to-offenses were associated with lower crime rates, other things equal—a finding supportive of the deterrence hypothesis.
Youth: Higher percentages of youth-to-population were positively associated with crime rates, a demographic relationship found consistently in most crime research.
Education spending: More government spending on education was negatively linked to crime rates, holding constant other factors, suggesting that efforts to build human capital might provide positive alternatives to illegitimate activity.
Bottom line: Improve clearance rates, support education, and watch the crime rate go down. Hopefully.
Next: How to improve clearance rates
Reference
Douglas Clement (2009) Just the facts, ma’am: Crime patterns in the district vary widely, but explaining differences and trends is difficult, The Region https://www.minneapolisfed.org/publications/fedgazette/just-the-facts-maam