Automatic Debiased Machine Learning of Causal and Structural Effects

TL;DR

This paper introduces an automatic debiasing method for high-dimensional regressions using machine learning, enabling valid inference for causal and structural effects without requiring full bias correction formulas.

Contribution

It provides a general, automatic debiasing approach compatible with various machine learning methods for estimating causal and structural effects.

Findings

Successfully applied to estimate treatment effects in NSW job training data.

Estimated demand elasticities from scanner data considering correlated preferences.

Provided robust standard errors and convergence rates for the debiased estimators.

Abstract

Many causal and structural effects depend on regressions. Examples include policy effects, average derivatives, regression decompositions, average treatment effects, causal mediation, and parameters of economic structural models. The regressions may be high dimensional, making machine learning useful. Plugging machine learners into identifying equations can lead to poor inference due to bias from regularization and/or model selection. This paper gives automatic debiasing for linear and nonlinear functions of regressions. The debiasing is automatic in using Lasso and the function of interest without the full form of the bias correction. The debiasing can be applied to any regression learner, including neural nets, random forests, Lasso, boosting, and other high dimensional methods. In addition to providing the bias correction we give standard errors that are robust to misspecification, convergence rates for the bias correction, and primitive conditions for asymptotic inference for estimators of a variety of estimators of structural and causal effects. The automatic debiased machine learning is used to estimate the average treatment effect on the treated for the NSW job training data and to estimate demand elasticities from Nielsen scanner data while allowing preferences to be correlated with prices and income.