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Chapter8.pptxChapter 8
Modeling Neighborhood Crime and Self-Enforcement
Introduction
Variation in crime rates can vary substantially across neighborhoods within a city.
This chapter lays out a theory of spatial variation of crime within a city – The Neighborhood Crime Model
As we will see, a large factor depends on involvement and cooperation of the general public. Citizens play a large role in the criminal justice system by reporting crime, providing evidence, and testifying against offenders.
Involvement of citizens has the power to raise the probability of conviction significantly as well as take measures to make offending more difficult and lower the gains/benefit to offenders.
The Neighborhood Crime Model
Image a city across which the sanctions for those convicted of a particular offender are identical and enforcement is the responsibility of a single police force. The city is divided into smaller neighborhoods based on topographic features, patterns of land use, and variations in settlement patterns – in other words, not based on crime rates.
This city would observe great variation in crime rates across neighborhood.
The Neighborhood Crime Model
Freeman, Grogger, and Sonstelie (1996) notes that
the expected loss per offense is high in areas of low crime.
in high crime areas, the conviction rate and the ratio of convictions to offenses is much lower.
More police effort is allocated towards neighborhoods with low crime
The Neighborhood Crime Model will help us understand these facts.
The Neighborhood Crime Model
At the neighborhood level, the gross return from crime varies along the demand curve. As offending increases, the expected return decreases since the best opportunities for crime are exhausted and potential victims take greater precautions as crime increases.
Additionally, in spatial models, at the neighborhood level, the probability of conviction is high when there are few offenders. In this situation, vigilance of citizens is very effective in finding and apprehending citizens.
The Neighborhood Crime Model
Schooling Effect - As the number of offenders in the area increases, the probability of conviction decreases because
Citizen cooperation becomes less effective as offenders increases.
Conviction requires that a particular crime is associated with a particular offense which becomes more difficult when there are many offenders.
The Neighborhood Crime Model
The number of offenders will either increase or decrease according to the difference in returns from the legal market wage and the net returns to crime
If W<h, then offending will increase
If W>h, then offending will decrease
What strategy could be used to reduce n** to n*?
The Neighborhood Crime Model
The neighborhood crime model also suggests two other crime-reduction strategies
Efforts to raise wages in legal employment shift W up
Efforts to organize neighborhood watch raise the probability of conviction and lower net returns to crime
Street Gangs
Thus far the model assumed that there is free entry and exit of crime.
Suppose there was a street gang that, through the use of force, had a monopoly on crime. What would be the equilibrium quantity of crime?
In this instance, the gang would choose the quantity of crime that maximized returns.
The Self-Enforcement Model
Enforcement of the criminal law can be enhanced by the cooperation and participation of the public.
Self-enforcement models are concerned with social situations in which private actions by individual citizens are sufficient to prevent or deter crime.
Individual citizens are often in a position to impose significant costs on potential offenders. For example, through surveillance or through intervention that deters crime or prevents it from escalating.
Practice Problem
Suppose the wage for drug dealing is given by H = 10N – N^2. The current number of drug deals is 2, and the current market legal wage is $9.
What is the current wage from drug dealing?
In the long run, what would you expect the equilibrium wage from drug dealing to be?
How many drug dealers would you expect there to be?
