The death penalty has fallen into disfavor in recent years.  But what’s the long-run trend?  I’ve intermittently wondered about this for over a decade.  Last night, I finally decided to check.

I found a time series of total U.S. executions from 1608-2002 here, broken down (roughly) by quarter-century.  I found a time series for long-run population here.  The numbers are irregular during the early centuries, with decennial censuses since 1790. 

Since the periods for the two series don’t perfectly match, I just use the population numbers closest to the final year of each quarter-century of executions.  For example, 1650-1674 had 49 executions, and the year closest to 1674 for which population data is available is 1670 (when population was 111,900). 

Here’s what I found:


The decline in executions per capita is perfectly monotonic.  Since executions are aggregated over quarter centuries, the pattern isn’t utterly amazing, but I was still shocked by its consistency.  In historical perspective, capital punishment virtually disappeared over a century ago, when its incidence approached one-in-a-million per year.  “Ideas have consequences,” you say?  Perhaps, but executions were in rapid decline long before liberal opponents of the death penalty began their crusade.

I can easily imagine my graph in a Julian Simon or Steven Pinker chapter on human progress and the decline in violence.  Even though I have no philosophical objection to the death penalty, it’s hard not to interpret this 400-year pattern as a strong sign of human betterment.  Anyone care to say nay?