Hat tip to Yglesias

Mark and I have been hard on Matt Yglesias lately.  But this post was a really clever idea.  He took Kevin Drum's idea that lead was responsible for a rise in violent crime and asked "if this explanation is correct then what else must be true?".  Since impulse control is also linked to high school graduation he plotted high school graduation (which has been unexpectely rising) and sees the same pattern as with violent crime. 

Now nothing rules out a confounder that affects both of these outcomes.  I worry about simple explanations for complex phenomena.  But it was a clever idea to try and falsify the hypothesis by looking at things that should be related to violent crime.  And, if there was going to be a candidate for such a broad level of toxicity, a substance implicated in brain damage going back to classical Rome isn't a bad choice.