An economist's perspective on Shadish (2010) and West and Thoemmes (2010).

In Shadish (2010) and West and Thoemmes (2010), the authors contrasted 2 approaches to causality. The first originated in the psychology literature and is associated with work by Campbell (e.g., Shadish, Cook, & Campbell, 2002), and the second has its roots in the statistics literature and is associated with work by Rubin (e.g., Rubin, 2006). In this article, I discuss some of the issues raised by Shadish and by West and Thoemmes. I focus mostly on the impact the 2 approaches have had on research in a 3rd field, economics. In economics, the ideas of both Campbell and Rubin have been very influential, with some of the methods they developed now routinely taught in graduate programs and routinely used in empirical work and other methods receiving much less attention. At the same time, economists have added to the understanding of these methods and through these extensions have further improved researchers' ability to draw causal inferences in observational studies.