Riesz representers for the rest of us

Abstract: The application of semiparametric efficient estimators, particularly those that leverage machine learning, is rapidly expanding within epidemiology and causal inference. Much of the recent methodological literature on these estimators relies heavily on the Riesz representation theorem and Riesz regression. This paper aims to introduce the Riesz representation theorem to an applied audience, explaining why and how Riesz regression is becoming widely used in the semiparametric estimator statistical literature.