Instrument-free inference under confined regressor endogeneity; derivations and applications

Instead of exploiting instruments and claiming these to be uncorrelated with the disturbances, in an instrument-free approach one may adopt flexible bounds on the correlation between the endogenous regressors and the disturbances. Such an alternative to Two-Stage Least-Squares (TSLS) inference is developed here for general linear models with endogenous possibly time-dependent regressors. Earlier results enabled this just for rather restrictive mesokurtic i.i.d. cross-section data. In three empirical replication studies their underlying exclusion restrictions are shown to be most doubtful. Next, incredible (weak-instrument robust) TSLS inference is replaced by more reliable remarkably narrow instrument-free asymptotically conservative confidence intervals.

C12, C13, C21, C22, C26

endogeneity robust least-squares inference, new exclusion restrictions test, replication studies, sensitivity analysis of two-stage least-squares