Bad Statistics About Bad Things

Critics of policing and mass incarceration make a basic statistical mistake.  Men represent less than half the population of the country but over 90% of those incarcerated.  But no one says the system is sexist.  That is because men commit more crime.  Comparing population numbers to incarceration rates gives a false picture.  Crime rates should be compared to incarceration rates.

Why are groups imprisoned at higher rates than their representation in the population?  The first question must be whether these groups are doing things that get you imprisoned at higher rates than their representation in the population.  Similarly situated groups can be compared. Groups that are not similarly situated cannot be compared. In America today, ethnic and racial groups are not similarly situated. There are many reasons for this, including the systemic racism of the recent past. The Jim Crow laws did not predestine anyone for a life of crime, but they didn’t help either. And there are many more reasons for ethnic and racial difference that are worth knowing. The rich and the poor are not similarly situated. I’ve read that the most predictive factor for criminality is age, then sex. Social scientists try to control for variables like relative crime rates. We should do the same, even though it is a difficult conversation to have.

Unfortunately, for many, the analysis goes something like this: look at the percentage of the population that belongs to the group, look at that group’s representation in prison, and draw a conclusion. Social scientists know better. The media should know better, and so should we.

Here’s how Crime and Consequences describes the problem:

One thing we do not need is the exaggeration of the prejudice problem created by all the bleating about “disparities” in statistics based on the Fallacy of the Irrelevant Denominator. Comparisons of the demographics of Statistic X with the general population are irrelevant if offending rates are not uniform across the demographic groups in question, which they rarely are. Do the police ticket more men than women for speeding? Of course they do, because a greater percentage of men speed. That statistic does not establish or even indicate discriminatory enforcement unless one establishes that speeding men are more likely to be ticketed than speeding women. The general population is an irrelevant denominator. The people who commit the offense in question make up the relevant denominator. And so it is for criminal justice statistics generally.

Public Defenders Play the Race Card

I just finished an article on Slate with the headline “When Race Tips the Scales in Plea Bargaining.”  It discusses a study out of Loyola Law school that

analyzed 30,807 misdemeanor cases in Wisconsin over a seven-year period and found that white people facing misdemeanor charges were more than 74 percent more likely than black people to have all charges carrying potential prison time dropped, dismissed, or reduced. And white people with no criminal history were substantially more likely to have charges reduced than black people who had no criminal history.

The authors did not consider the obvious: that relative poverty might cause this outcome.  In California, people of color are less wealthy.  If you wealthy, you are more likely to afford a lawyer who can negotiate these benefits.  They wealthy can bail themselves out and fight the case, eventually securing a better deal.  If people of color tend to be less wealthy, they may be unable to afford to fight as hard, and thus may get a worse deal.  There may be other explanations. Do the two groups commit the same crimes at the same rates? Consider a hypothetical: one group commits only driving without a license misdemeanors, while the other commits only domestic violence misdemeanors. You would not expect similar jail commitment rates for these two groups. The authors don’t consider whether different patterns of offending account for the different outcomes. The authors don’t consider geographical differences. Is the law more lenient in the suburbs than urban centers? In the south than the north? The list of alternate explanations could go on and on.

But the authors, without an explanation, go right to “prosecutors are racist” as an explanation.  That’s lazy, inaccurate, and offensive to well-meaning public servants. Prosecutors are like any other profession, there are good and bad people. In my experience, prosecutors as a group far exceed other lawyers in their honesty and ethical conduct. And they show a lot of patience in the face of nonsense muckraking like this, both inside and outside of courtroom.

Also, the incoherent authors appear to partially blame bail, but don’t explain how the race-neutral bail system fits their “prosecutors are racist” theory.  Is it bail that’s causing this?  Or racist prosecutors?  The authors can’t decide.  They just know that prosecutors “destroy livelihoods, and tear families apart” “destroy communities of color” and “devastate low-income communities.”  Not criminals; prosecutors are to blame.  Who thinks like this?  More stupidity: the study found disparities in Wisconsin, therefore “New York must eliminate money bail.”  What?

I just hate-read this again before finishing up and noticed this was written by public defenders.  Assuming they believe in their work, their agenda is clear. Not all public defenders make dumb, incoherent arguments.  Not all public defenders are quick to accuse the other side of racism.  But it seems like these two are a great example of everything that’s wrong with the defense bar.

232 Burglaries

If you google “individual offense rates”, you’re going to get a lot of basketball statistics.  But the phrase is used in Thinking About Crime, a book I’ve been reading in order to educate myself on criminology.  It’s funny that no formal information about criminology is given to prosecutors in my office.  More time is spent on learning the elements of a crime and practicing trial skills.  Prosecutors are key actors in the criminal justice system, wielding the massive, grinding power of state coercion, faced everywhere with choices that affect years of people’s lives.  This system is studied in detail by academics, economists, statisticians, and others.  But we make our choices with little to no knowledge of criminology, instead relying on our gut feeling, what we have heard from others, rules of thumb, and other unreliable sources.  Judges are the same.

The primary penalty that felony prosecutors impose is state prison.  It is the archetypal consequence for crime.  We send felons there as retribution, to incapacitate them, and for deterrence to other criminals. Retribution seems to many like a fancy way of saying “legitimate revenge.”  To me, it has a dark, primal connotation.  We can’t measure it with statistics.  There is no number showing how many sentence per year result in appropriate retribution.  Deterrence is easier to measure, but still not easy to measure.  “It is the mark of an educated man to look for precision in each class of things just so far as the nature of the subject permits.”

It’s incapacitation that jumped out at me from the pages of Thinking About Crime.  Incapacitation seems capable of measurement.  It is not dark and primal, like state-sponsored revenge, and it is at the heart of our current “mass incarceration” controversy.  Wilson opens the subject with his typical clarity.

“To determine the amount of crime that is prevented by incarcerating a given number of offenders for a given length of time, the key estimate we must make is the number of offenses a criminal commits per year free on the street.”

(Wilson, Thinking About Crime (1975) p. 135.)

“The individual offense rate varied significantly for different kinds of offenders.  For example, it was highest for larceny and lowest for aggravated assault.”  (Wilson, Thinking About Crime (Rev. Ed. 1975) p. 137; citing Alfred Blumstein and Jacqueline Cohen, “Estimation of Individual Crime Rates From Arrest Records,” Journal of Criminal law and Criminology 70 (1979), p. 585.)  In this study, adults who had been arrested at least twice in Washington D.C. committed between nine and 17 serious offenses per year while free.  (Ibid.)  “Serious” in this context means murder, aggravated assault, forcible rape, robbery, burglary, larceny, and auto theft.

The studies cited by Wilson are as old as his book, but he does have some California numbers.  The Rand Group has found that the average California prisoner had committed about 14 serious crimes per year over three years of freedom.  (Peterson & Braiker, Doing Crime (1980) pp. vii, 32.)  The number is shockingly high.  Wilson also uses California statistics to return to one of his favorite themes, that crime may be impossible to prevent.  He points out that Rand also found that if no one were confined in prison, the number of armed robberies in California would be about 22% higher than it is now.  (Ibid.)  I think this might be a low estimate, since it does not account for the effect of deterrence: if prison were taken off the table the streets would be a consequence free environment on the streets.

Many of these statistics rely on interviews with convicts.  A person serving time in California for robbery would on average admit to committing 53 robberies per year free.  Burglars reported committing on average 90 burglaries per year.  (Wilson, Thinking About Crime (Rev. Ed. 1975) p. 137; citing Peter W. Greenwood, Selective Incapacitation (1982) pp. 43-44.)

As I read these numbers, I was blown away by how frequently a criminal would commit crimes.  I was already aware, from sources such as the National Crime Victimization Survey, that most crime goes unreported, and that the vast majority of reported crime goes unsolved.  Those facts tend to imply that a lot of crime is going on out there compared to arrests and convictions.  But it’s one thing to suspect that fact from the aggregate numbers.  It’s another thing entirely to see what each individual is doing.  Especially because I primarily deal with individuals each day: individual cases and individual victims.

Wilson’s discussion of career criminals was particularly sobering.  he points out that average rate numbers are not very useful because a small number of offenders commit a very large number of offenses.  The median number of burglaries committed by the inmates in the Rand study was five per year, but the 10% of inmates who were the highest-rate offenders committed on average of 232 burglaries a year.  The median number of robberies was also about 5 a year, but the top 10% of offenders committed an average of 87 a year.  Incarcerating one robber who was among the top 10% in offense rates would prevent more robberies than incarcerating 18 offenders who were at or below the median.  (Peter W. Greenwood, Selective Incapacitation (1982) pp. 43-44, 46.)

We don’t learn much about criminology in training.  But if we learned the cold hard facts about the poisonous effect that career criminals have in our communities, and the salutary effect of removing them, we might be a little more motivated to go out and get them.  I read RAP sheets.  I read probation reports.  But reading Wilson has taught me the importance of using these things to put the full weight of the power of the state towards incapacitating career criminals.


Wilson’s numbers, and the numbers he relied upon, are old. Alex Piquero and Alfred Blumstein have newer numbers in their 2007 paper.

Longer Sentences Reduce Recidivism

At a courthouse in Seattle, Washington, defendants who plead guilty prior to trial are randomly assigned to a different sentencing judges.  These judges, as you would expect, have a range of ideas about sentencing.  Some are more likely to hand down prison time than others.  The luck of the draw can have a great effect on a defendant, who is understandably hoping for a lenient judge.  Moving from the most lenient judge to the harshest judge could double an offender’s sentence length.

This sentencing scheme is also fertile ground for researchers who want to study the effect of prison sentence length on recidivism.  Michael Roach and Max Schanzenbach, professors of economics and law respectively, studied the sentencing variations in this courthouse.  They found that “one-month extra prison sentence reduces the rate of recidivism by about one percentage point, with possibly larger effects for those with limited criminal histories.”

The authors caution that “extra prison time does not yield a statistically significant reduction in recidivism for offenders with more significant criminal histories.  They also note that they only studied relatively short sentences.  “The average sentence length in the data is nine months, and the median sentence is three months.  Thus, the results pertain only to low-level offenders mostly convicted of non-violent property crimes.”

Even with these caveats, this study has broad application for prosecutors and judges at sentencing.  Reducing recidivism is one of the chief goals of the criminal justice system.  This study seems to provide a clear way to do it.  Many defense attorneys believe that it is in the best interest of their client to obtain the shortest possible period of incarceration.  This study proves that belief wrong in many cases.  Judges should take note that they can rehabilitate a prisoner and reduce his recidivism rate simply by giving him more prison time at the outset.  This approach is backed up by more than slogans like “tough love.”  It’s now backed up by hard data.  And in addition to its rehabilitative benefit, additional jail time also accomplishes the purposes of general deterrence and rehabilitation.

I hope the criminal justice system takes note of this data.  Maybe we can improve the way we protect our communities while at the same time rehabilitating defendants.