omitted variable bias is not a kind of nitpick. Omitted variable bias when it comes to human systems is massive. And you can show over and over again this is true. Russ: Explain what omitted variable bias is. What do you mean that? Guest: What I mean by that is if I have a regression analysis that tries to predict a set of variables- - http://www.econtalk.org/archives/2012/06/manzi_on_knowle.html