Sunday, June 06, 2004

Steven Landsburg e-mail #2

Thanks for your thoughtful reply. A few remarks:

1) There is reasonably good evidence that enacting a capital
punishment law has no effect on murder rates, and very good
evidence that increasing the number of executions has a very
strong effect on murder rates.

I know of only one careful study that finds otherwise regarding
executions, and that's the work of Steve Levitt and coauthors.

There's also a very interesting paper by Ed Leamer where he
tries the experiment of first biasing his methods as strongly
as possible in favor of finding a deterrent effect and then as
strongly as possible in the opposite direction. In the first
case he finds that each execution prevents 13 murders; inthe
second case he finds that each execution *causes* 3 murders.
But nearly every unbiased study gets numbers in the 8-10 range.
Again, Ehrlich is the big name in the field and it is worth
noting that he is very opposed to capital punishment.

2) If the bulk of the evidence pointed to no deterrent
effect, I would certainly oppose capital punishment, with great


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