Brittany and Michael Introduce: Five Pioneers in Instrumental Variables

Brittany and Michael are back with another series, this time entitled “Five Pioneers in Instrumental Variables”. What’s instrumental variables? Well according to them, it’s when one irrelevant thing does something to some second thing a second thing so we know how the second thing changes the third thing.” Couldn’t have said it better myself. Arguably, instrumental variables is one of the most important tools in the causal inference toolbox, and while it has its detractors, it was given some love not too long ago by a Swedish bank.

In this series, Brittany and Michael start out with a father-son team, Philip and Sewell Wright, as the progenitors of this important method in causal inference.¹ Philip was the father, an economist and renaissance man who was very concerned about tariffs — so much so that it co-invented instrumental variables to analyze their effect in a riveting book, The Tariff on Animal and Vegetable Oils. The actual proof and explanation of Wright’s instrumental va…