<b>MatchIt</b>: Nonparametric Preprocessing for Parametric Causal Inference

Abstract

<b>MatchIt</b> implements the suggestions of Ho, Imai, King, and Stuart (2007) for improving parametric statistical models by preprocessing data with nonparametric matching methods. <b>MatchIt</b> implements a wide range of sophisticated matching methods, making it possible to greatly reduce the dependence of causal inferences on hard-to-justify, but commonly made, statistical modeling assumptions. The software also easily fits into existing research practices since, after preprocessing data with <b>MatchIt</b>, researchers can use whatever parametric model they would have used without <b>MatchIt</b>, but produce inferences with substantially more robustness and less sensitivity to modeling assumptions. <b>MatchIt</b> is an R program, and also works seamlessly with <b>Zelig</b>.