Crimes down, Convictions ... up!

Crime rates in the United States have been plummeting for over 20 years. The cause of this turnaround is a topic of much debate and controversy. The Freakonomics guys say we can thank Roe v. Wade. Kevin Drum says we can thank unleaded gas. The authoritarians say we can thank boots on the ground and pigs in the pen. And there are many other plausible theories. Perhaps the most plausible theory is that a lot of things came together at once. But no one denies that we've seen a remarkable and remarkably unexpected drop in crime—all kinds of crime: rape, murder, theft, etc.

This got me to thinking. Even though you hear more and more about this dropping crime rate, you don't hear much about prosecutors sitting around on their hands with nothing to do. So I wondered whether there was any data on the relationship between the number of crimes committed and the number of people who are actually being convicted of crimes.

Although I'm sure such data exists, I couldn't find it on the Google. So I had to create it myself:

The red line is the crime rate in years 1995 through 2011. You can see there is a precipitous decline. The source for this data is the US Department of Justice.

The green line is the number of people convicted of crimes in federal court in years 1995 through 2011. The source for this data is the United States Sentencing Commission.

What you see, obviously, is a remarkable mismatch. As the crime rate goes down, the number of people convicted of crimes goes up.

Now, one obvious objection to this graph is that it comparing apples to oranges: all crimes versus federal convictions. And that's true. So one possible explanation for this mismatch is that federal crimes have expanded despite the overall fall in the crime rate. But my working assumption is that the federal conviction data is a good proxy for the overall state and federal conviction rate. (Some support for my assumption is provided by the fact that overall incarceration rates continued to rise even while crime rates plummeted.)

Anyhow, you can draw your own conclusions. My conclusion is the obvious one: criminal justice is a one-way ratchet.