Finite Sample Inference for Quantile Regression Models
Massachusetts Institute of Technology (MIT) - Department of Economics; New Economic School
University of Chicago Graduate School of Business
University of California, Berkeley - Department of Economics
January 31, 2006
MIT Department of Economics Working Paper No. 06-03
Under minimal assumptions finite sample confidence bands for quantile regression models can be constructed. These confidence bands are based on the "conditional pivotal property" of estimating equations that quantile regression methods aim to solve and will provide valid finite sample inference for both linear and nonlinear quantile models regardless of whether the covariates are endogenous or exogenous. The confidence regions can be computed using MCMC, and confidence bounds for single parameters of interest can be computed through a simple combination of optimization and search algorithms. We illustrate the finite sample procedure through a brief simulation study and two empirical examples: estimating a heterogeneous demand elasticity and estimating heterogeneous returns to schooling. In all cases, we find pronounced differences between confidence regions formed using the usual asymptotics and confidence regions formed using the finite sample procedure in cases where the usual asymptotics are suspect, such as inference about tail quantiles or inference when identification is partial or weak. The evidence strongly suggests that the finite sample methods may usefully complement existing inference methods for quantile regression when the standard assumptions fail or are suspect.
Number of Pages in PDF File: 39
Keywords: Quantile Regression, Extremal Quantile Regression, Instrumental Quantile Regression
JEL Classification: C1, C3
Date posted: February 3, 2006
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