We present response surface coefficients for a large range of quantiles of the Elliott, Rothenberg and Stock (Econometrica, 1996) DF-GLS unit root tests, for different combinations of the number of observations and the lag order in the test regressions, where the latter can be either specified by the user or endogenously determined. The critical values depend on the method used to select the number of lags. The Stata command ersur is presented, and its use illustrated with an empirical example that tests the validity of the expectations hypothesis of the term structure of interest rates.
