TY - JOUR T1 - A Practitioner’s Guide to Cluster-Robust Inference JF - Journal of Human Resources JO - J Hum Resour SP - 317 LP - 372 DO - 10.3368/jhr.50.2.317 VL - 50 IS - 2 AU - A. Colin Cameron AU - Douglas L. Miller Y1 - 2015/03/31 UR - http://jhr.uwpress.org/content/50/2/317.abstract N2 - We consider statistical inference for regression when data are grouped into clusters, with regression model errors independent across clusters but correlated within clusters. Examples include data on individuals with clustering on village or region or other category such as industry, and state-year differences-in-differences studies with clustering on state. In such settings, default standard errors can greatly overstate estimator precision. Instead, if the number of clusters is large, statistical inference after OLS should be based on cluster-robust standard errors. We outline the basic method as well as many complications that can arise in practice. These include cluster-specific fixed effects, few clusters, multiway clustering, and estimators other than OLS. ER -