Studies say death penalty deters crime

[Ban Hammer 12,901]

Anti-death penalty forces have gained momentum in the past few years, with a moratorium in Illinois, court disputes over lethal injection in more than a half-dozen states and progress toward outright abolishment in New Jersey.

The steady drumbeat of DNA exonerations — pointing out flaws in the justice system — has weighed against capital punishment. The moral opposition is loud, too, echoed in Europe and the rest of the industrialized world, where all but a few countries banned executions years ago.

What gets little notice, however, is a series of academic studies over the last half-dozen years that claim to settle a once hotly debated argument — whether the death penalty acts as a deterrent to murder. The analyses say yes. They count between three and 18 lives that would be saved by the execution of each convicted killer.

The reports have horrified death penalty opponents and several scientists, who vigorously question the data and its implications.

So far, the studies have had little impact on public policy. New Jersey's commission on the death penalty this year dismissed the body of knowledge on deterrence as "inconclusive."

But the ferocious argument in academic circles could eventually spread to a wider audience, as it has in the past.

"Science does really draw a conclusion. It did. There is no question about it," said Naci Mocan, an economics professor at the University of Colorado at Denver. "The conclusion is there is a deterrent effect."

A 2003 study he co-authored, and a 2006 study that re-examined the data, found that each execution results in five fewer homicides, and commuting a death sentence means five more homicides. "The results are robust, they don't really go away," he said. "I oppose the death penalty. But my results show that the death penalty (deters) — what am I going to do, hide them?"

Statistical studies like his are among a dozen papers since 2001 that capital punishment has deterrent effects. They all explore the same basic theory — if the cost of something (be it the purchase of an apple or the act of killing someone) becomes too high, people will change their behavior (forego apples or shy from murder).

To explore the question, they look at executions and homicides, by year and by state or county, trying to tease out the impact of the death penalty on homicides by accounting for other factors, such as unemployment data and per capita income, the probabilities of arrest and conviction, and more.

Among the conclusions:

• Each execution deters an average of 18 murders, according to a 2003 nationwide study by professors at Emory University. (Other studies have estimated the deterred murders per execution at three, five and 14).

• The Illinois moratorium on executions in 2000 led to 150 additional homicides over four years following, according to a 2006 study by professors at the University of Houston.

• Speeding up executions would strengthen the deterrent effect. For every 2.75 years cut from time spent on death row, one murder would be prevented, according to a 2004 study by an Emory University professor.

In 2005, there were 16,692 cases of murder and nonnegligent manslaughter nationally. There were 60 executions.

The studies' conclusions drew a philosophical response from a well-known liberal law professor, University of Chicago's Cass Sunstein. A critic of the death penalty, in 2005 he co-authored a paper titled "Is capital punishment morally required?"

"If it's the case that executing murderers prevents the execution of innocents by murderers, then the moral evaluation is not simple," he told The Associated Press. "Abolitionists or others, like me, who are skeptical about the death penalty haven't given adequate consideration to the possibility that innocent life is saved by the death penalty."

Sunstein said that moral questions aside, the data needs more study.

Critics of the findings have been vociferous.

Some claim that the pro-deterrent studies made profound mistakes in their methodology, so their results are untrustworthy. Another critic argues that the studies wrongly count all homicides, rather than just those homicides where a conviction could bring the death penalty. And several argue that there are simply too few executions each year in the United States to make a judgment.

"We just don't have enough data to say anything," said Justin Wolfers, an economist at the Wharton School of Business who last year co-authored a sweeping critique of several studies, and said they were "flimsy" and appeared in "second-tier journals."

"This isn't left vs. right. This is a nerdy statistician saying it's too hard to tell," Wolfers said. "Within the advocacy community and legal scholars who are not as statistically adept, they will tell you it's still an open question. Among the small number of economists at leading universities whose bread and butter is statistical analysis, the argument is finished."

Several authors of the pro-deterrent reports said they welcome criticism in the interests of science, but said their work is being attacked by opponents of capital punishment for their findings, not their flaws.

"Instead of people sitting down and saying 'let's see what the data shows,' it's people sitting down and saying 'let's show this is wrong,'" said Paul Rubin, an economist and co-author of an Emory University study. "Some scientists are out seeking the truth, and some of them have a position they would like to defend."

The latest arguments replay a 1970s debate that had an impact far beyond academic circles.

Then, economist Isaac Ehrlich had also concluded that executions deterred future crimes. His 1975 report was the subject of mainstream news articles and public debate, and was cited in papers before the U.S. Supreme Court arguing for a reversal of the court's 1972 suspension of executions. (The court, in 1976, reinstated the death penalty.)

Ultimately, a panel was set up by the National Academy of Sciences which decided that Ehrlich's conclusions were flawed. But the new pro-deterrent studies haven't gotten that kind of scrutiny.

At least not yet. The academic debate, and the larger national argument about the death penalty itself — with questions about racial and economic disparities in its implementation — shows no signs of fading away.

Steven Shavell, a professor of law and economics at Harvard Law School and co-editor-in-chief of the American Law and Economics Review, said in an e-mail exchange that his journal intends to publish several articles on the statistical studies on deterrence in an upcoming issue.

link

[natty bumppo 289]

Interesting read ...

[Trumplestiltskin 5,791]

Interesting - but nothing really new. Some counterpoints.

Sociological Realities and Econometric Illusions

New Claims About Execution and Deterrance

The second article actually references Mocan's work.

[w¡n9Nµ7 §£@¥€r 123]

So what if there is a deterrent effect? That's why not the death penalty is wrong. The death penalty is wrong because it is murder.

[Ban Hammer 12,901]

So what if there is a deterrent effect? That's why not the death penalty is wrong. The death penalty is wrong because it is murder.

mur·der (mûrdr) KEY

NOUN:

The unlawful killing of one human by another, especially with premeditated malice.

the story isn't about murder

[w¡n9Nµ7 §£@¥€r 123]

Matter of opinion - I'd say any immoral or unjust taking of life is murder. The death penalty certainly qualifies. The fact that it's not unlawful means little. Many laws are unjust and immoral.

[Ban Hammer 12,901]

Matter of opinion - I'd say any immoral or unjust taking of life is murder. The death penalty certainly qualifies. The fact that it's not unlawful means little. Many laws are unjust and immoral.

agreed.

[dalegg 143]

"If it's the case that executing murderers prevents the execution of innocents by murderers, then the moral evaluation is not simple," he told The Associated Press. "Abolitionists or others, like me, who are skeptical about the death penalty haven't given adequate consideration to the possibility that innocent life is saved by the death penalty."

Meaning you've completely ignored the other side of the argument because you've already made your mind up. At least he admits it.

[Ban Hammer 12,901]

"If it's the case that executing murderers prevents the execution of innocents by murderers, then the moral evaluation is not simple," he told The Associated Press. "Abolitionists or others, like me, who are skeptical about the death penalty haven't given adequate consideration to the possibility that innocent life is saved by the death penalty."

Meaning you've completely ignored the other side of the argument because you've already made your mind up. At least he admits it.

and for that matter, shuffle the words around a bit and you get this....which quite a few anti-death penalty people would rather die than admit.

If it's the case that executing murderers prevents the execution of innocents by murderers, then the moral evaluation is not simple," he told The Associated Press. "Abolitionists or others, like me, who are skeptical about the death penalty haven't given adequate consideration to the possibility that the death penalty saves innocent life

Edited June 11, 2007 by charlesandnessa

[Hilarious Clinton 452]

I think the never ending supply of butt sex leading up to the execution is the real deterrent.

[Trumplestiltskin 5,791]

Here's a statistician's comments on that:

The conclusions that follow from the analyses are straightforward. From

1977 to 1997, most states during most years executed no one. A few states

on rare occasion executed up to 5 individuals in a particular year. Years

with 5 executions or less represent 99% of the data. Limiting the analysis to

these 99% of the observations, there is no evidence of a negative relationship

between the number of executions lagged by one year and either the homicide

rate or the number of homicides. Including the 11 execution extreme values

can for some analyses suggest possible negative effect, but only for these 11

observations and only if one ignores the very wide confidence intervals.

Imposing a linear relationship between executions and either the number

of homicides or the homicide rate, and including the 11 extreme values, can

for some analyses generate the appearance of deterrence effects much like

those recently reported. But the linear relationship is contradicted by the

data, and any hint of deterrence disappear if the 11 observations are excluded

from the analysis. There is also no evidence in these data that replacing the

number of executions with an indicator variable coded “0” for no executions

and “1” for 1 or more executions changes the overall conclusions.

All of the points made about the 11 extreme values apply to the data

from Texas. Moreover, a simple simulation demonstrates that even when one

knows for certain that in the 49 other states executions are on the average

unrelated to the homicide rate, including the data from Texas can give the

false impression that a deterrence relationship exists.

The distributional problems that characterize the number of executions

remain when counties are the spatial units and/or months are the temporal

units. Disaggregating the data does not make the skewing disappear, and

can actually introduce a new set of difficulties. More elaborate estimation

procedures only paper paper over the problems and introduce a new layer of

dubious assumptions.

Whatever one makes of those 11 observations, it would be bad statistics

and bad social policy to generalize from the 11 observations to the remaining

989. So, for the vast majority of states for the vast majority of years, there

is no evidence for deterrence in these analyses. And even for the remaining

11 observations, the credible evidence is for deterrence is lacking.

The analyses reported here are hardly exhaustive and are perhaps affected

by misunderstandings about the data provided, or by errors in the data

themselves. Nevertheless, the results raise serious questions about whether

anything useful about the deterrent value of the death penalty can ever be

learned from an observational study with the data that are likely to be available.

With an intervention that is so highly skewed, a very small portion of

the data will likely impart significant influence on the results. Generalizations

to the mass of the data then become very risky. It is difficult to imagine

how such problems can be overcome no matter how skilled or sophisticated

the data analyst.

Finally, the focus in this paper has been in the role of influential observations

because their impact is well understood in the statistical literature and

because in this instance, the errors that can result are easily demonstrated.

But as noted in the introduction, there are many other statistical problems

could have been tackled.

[Mr. Big Dog 10,747]

Here's a statistician's comments on that:

All of the points made about the 11 extreme values apply to the data

from Texas. Moreover, a simple simulation demonstrates that even when one

knows for certain that in the 49 other states executions are on the average

unrelated to the homicide rate, including the data from Texas can give the

false impression that a deterrence relationship exists.

Ah, Texas. Texas is very actively putting down anyone it can get it's hands on, yes? And yet, Houston (city in Texas last time I checked), made a top ranking (No. 2) on the list of cities with the highest homicide rates. Some deterrent...

Edited June 11, 2007 by ET-US2004

[Dan J 277]

Doing something about poverty will probably deter much more crime than a death penatly ever would.

I'm really mixed about the death penalty. Sometimes I feel that its justified, sometimes not. Sometimes I feel that its just a scapegoat to avoid facing the real problems.

[homesick_american 1]

Here's a statistician's comments on that:

All of the points made about the 11 extreme values apply to the data

from Texas. Moreover, a simple simulation demonstrates that even when one

knows for certain that in the 49 other states executions are on the average

unrelated to the homicide rate, including the data from Texas can give the

false impression that a deterrence relationship exists.

Ah, Texas. Texas is very actively putting down anyone it can get it's hands on, yes? And yet, Houston (city in Texas last time I checked), made a top ranking (No. 2) on the list of cities with the highest homicide rates. Some deterrent...

Harris County is by far the number one supplier of inmates to death row, and it also has one of the highest violent crime rates in the USA. I agree...some deterrent.

[dalegg 143]

Ah, Texas. Texas is very actively putting down anyone it can get it's hands on, yes? A

From 1976 to 2005 there were 55,922 murders in Texas and 385 executions. That is comes out to a rate of 0.69%. I don't think .69% qualifies as anyone it can get it's hands on.

Edited June 11, 2007 by dalegg