This article reviews Mostly Harmless Econometrics: An Empiricist's Companion, by Joshua D. Angrist and Jorn-Steffen Pischke.

Ordinary least squares (OLS) is omnipresent in regression modeling. Occasionally, least absolute deviations (LAD) or other methods are used as an alternative when there are outliers. Although some data adaptive estimators have been proposed, they are typically difficult to implement. In this...