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Justice Lab

The Tricky Business of Measuring Crime and Punishment

Pew researchers release a new prison scorecard, but it ain’t perfect.

One of the most widely cited figures in criminal justice is America’s incarceration rate. About 2.2 million people were in our prisons and jails in 2014, or 900 for every 100,000 adults in the country, the highest of any major country on earth.

For years, criminal justice wonks (including here at The Marshall Project) have yearned for metrics that would tell us more: Are we locking up the truly dangerous criminals? Is the system working? How is California doing relative to Texas or Pennsylvania?

On Wednesday, the Pew Charitable Trusts and its Public Safety Performance Project offers what it calls “a more nuanced assessment” of punishment. Rather than measuring the ratio of inmates to residents of a given jurisdiction, it measures the ratio of inmates to serious crime.

“Using the punishment rate to examine the U.S. criminal justice system, Pew found that all states became more punitive from 1983 to 2013, even though they varied widely in the amount of punishment they imposed,” the report says. In 37 states the “punitiveness” more than doubled.

It’s an interesting thought experiment, but it underscores how complicated and difficult it is to really measure the effectiveness of our criminal justice system.

We’ve grown accustomed to a quantified world of ever more complicated data available at our fingertips, on everything from how we sleep and eat to how often left-handed pinch hitters hit ground rule doubles on rainy days.

“The incredible databases of what we have for sports just blow away anything there is in criminal justice. It's kind of crazy,” said Adam Gelb, director of Pew’s Public Safety Performance Project, adding, “We can't answer some of the most basic questions about one of the most important functions of a society.”

Nearly five years ago, Gelb and Pew started by looking at recidivism — how often people released from prisons are arrested again for new offenses. But using recidivism alone to compare how states are doing at rehabilitating prisoners fell short. One state could have a lower recidivism rate simply because it tended to have more low risk offenders in its prisons. So then, Gelb said he began thinking about how to assess whether the “right” people are in prison, that is the serious, violent and repeat offenders most likely to commit new crimes.

Pew’s punishment rate focuses on the most serious felony offenses that lead to a year or more in state prison. The calculation divides each state’s imprisonment rate in a given year by the rate of crimes reported there, using the FBI’s Uniform Crime Reporting system. To account for some crimes being more serious and more likely to lead to longer prison sentences, Pew weights the annual crime rates by calculating the average time served for those crimes each year. After all of these calculations, Pew found that as America's imprisonment rate has gone up in the past three decades and as crime has dropped, the “punishment rate” rose by 165 percent.

While the methodology makes sense and is probably the best available considering the shortcomings of federal crime data, the punishment rate is not yet the magic metric. Unpacking the components of Pew’s punishment rate illustrates how tricky measuring criminal justice progress can be. The punishment rate depends on the number of crimes reported by the FBI. But the Uniform Crime Report, created in the 1920s, tracks only seven key crimes: murder, assault, rape, robbery, arson, burglary, larceny, motor vehicle theft. It excludes dozens of offenses — most notably drug crimes, which have been a major factor in the growth of prison populations. Pew’s report readily acknowledges that the Uniform Crime Report omits crimes for which roughly one-fifth of state prisoners are serving time.

“What that means is not to say that drug trafficking is not a serious crime, just that it's not reported and tracked in a way that you can support adding it to this formula,” Gelb said. “It does mean that — other things being equal — a state that has a lot of drug enforcement activity and stiff sentencing for drug offenses will have a higher punishment rate.”

The other trouble with the punishment rate is in the lag between crime and judgment. Pew is comparing the crime rate each year to the current prison population at that moment. It doesn't account for the people being sentenced each year or the prison intakes. It also doesn't look at what crimes those in prison were convicted of. So there is an inherent lag between when crimes happen and when someone might go to prison for them. Despite plummeting crime since the 1990s, the growth in the punishment rate didn’t overtake the rise in imprisonment until 2011. That may be partially explained by the gap in time between crime and incarceration, though Gelb contends that effect is ameliorated by calculating rolling averages for offense severity (but not the crimes themselves or the imprisonment rate). He said the adjustment is meant to be a barometer of the seriousness of crimes in a year rather than a “fine-tuned calculation.” But that lack of precision could undercut Pew’s implicit argument that in some states we are “punishing for punishment’s sake.”

Gelb concedes that the new report tries to shine a light on just one piece of a complicated system, and that it doesn’t explicitly factor in arrests, convictions or sentencing. But he hopes that the punishment rate will help start conversations among policymakers that a simple incarceration rate won’t.

“Our aspiration for the report is that states will take a look at these numbers and try to unpack what they mean,” said Gelb. “Even though the data is imperfect, it brings us a big step closer to understanding how states are using prisons.”