"Levitt wrote that Roe is "like the proverbial butterfly that flaps its wings on one continent and eventually creates a hurricane on another." He ought to be more careful with his similes: Surely he knew that he was echoing meteorologist Edward Lorenz's famous evocation of a global climate system--one that had such a dense web of interconnected pathways of causation that it made long-term weather forecasting a fool's errand. The actual event that inspired this observation was that, one day in 1961, Lorenz entered .506 instead of .506127 for one parameter in a climate-forecasting model and discovered that it produced a wildly different long-term weather forecast. This is, of course, directly analogous to what we see in the abortion-crime debate: Tiny changes in the data set yield vastly different results. This is a telltale sign (as if another were needed) that human society is far too complicated to yield to the analytical tools that Lott and Levitt bring to bear. Nobody in this debate has any reliable, analytically derived idea of what impact abortion legalization has had on crime. "I didn't know that about the famous "butterfly in Brazil" effect, but that is what I've been saying about Levitt's abortion-crime theory since 1999: it's beyond the power of contemporary social science to determine.
September 11, 2007
In National Review, Jim Manzi reviews economist John R. Lott's Freedomomics and takes a look at Steven D. Levitt's Freakonomics as well: