One way of determining how effective police are at solving crimes is to look at clearance rates. Clearance rates are generated by dividing the number of arrests police make for a particular crime by the actual number of times the crime was committed. In theory, a high clearance rate indicates that police are apprehending a large percentage of criminals.
For its yearly Uniform Crime Reports, the FBI estimates the amount of crime in the US by totaling all crimes discovered by police and all crimes reported to the police by the public. The Bureau also records the number of arrests made by police which are then used to generate clearance rates for a number of different crimes. The FBI’s clearance rates for 2009 suggest that police failed to solve more than 30% of criminal homicides, nearly 60% of forcible rapes, more than 70% of robberies, more than 40% of aggravated assaults, and nearly 90% of burglaries and motor vehicle thefts.
These numbers are useful, but I wanted to get a visual representation of the proportion of crimes being cleared, so I created a graphic (below) using the 2009 data for the major violent crimes (murder and nonnegligent manslaughter, forcible rape, robbery, and aggravated assault) and property crimes (burglary, larceny-theft, motor vehicle theft, and arson) that are tracked by the FBI. The red represents reports of crime while the blue represents arrests. If you’re confused about what any of the terms I’m using mean, you should check out this page for definitions.
This graphic is actually rather generous to law enforcement. Obviously not everyone the police arrest is actually guilty so it’s wrong to treat every arrest as a true clearance. Furthermore, since UCR data is based on reports of crime and many crimes go unreported, the FBI’s numbers tend to underestimate the actual amount of crime which leads to better clearance rates. Despite the fact that this data paints an unrealistically good picture of police performance, it makes it quite clear that police only manage to solve an abysmally small portion of violent crimes and property crimes.
Why would that be? Well, there are undoubtedly a number of factors at work, but I suspect one important reason is that the police have other priorities. Police spend so much time enforcing laws that criminalize victimless behaviors that it substantially eats into the time they would otherwise spend investigating real crimes.
Just look at the FBI’s arrest statistics. Despite the millions of violent crimes and property crimes that went unsolved last year, police found the time to arrest more than a million and a half people for bogus drug “crimes,” more than half a million people for violating liquor laws, more than a hundred and fifty thousand for possessing “illegal weapons,” and more than ten thousand people for gambling. Countless others were arrested for participating in consensual sex acts, being drunk in public, violating government-imposed curfews, and other absurd charges. Police even arrested nearly two thousand people who were never charged with any crimes at all.
Does anyone really believe that it makes sense for police to arrest millions of peaceful drug users and other victimless offenders when the same resources could be used to investigate murders, rapes, robberies, etc. — crimes that actually have suffering human victims — that they are currently failing to solve?