The data and programs for this paper can be obtained, typing 'Myoung-jae Lee' in Google and clicking on 'Instrument Residual Estimator'. The programs are written in 'GAUSS'; a 2-week trial version is available freely at www.aptech.com. For some inverse-weighting estimators, a tuning constant τ to prevent division by 0 is needed; there is no single best τ, but τ = 0.001 or 0.01 are used. Also, to improve finite-sample performance of some estimators, an integer q = 0, 1, 2, … is chosen, where q is not a tuning constant as the estimators are consistent for any q; q = 0 or 2 is used in this paper, and q = 2 or 3 is recommended.