On the Inconsistency of Instrumental Variables Estimators for the Coefficients of Certain Dummy Variables

David Giles

No 1106, Econometrics Working Papers from Department of Economics, University of Victoria

Abstract: In this paper we consider the asymptotic properties of the Instrumental Variables (IV) estimator of the parameters in a linear regression model with some random regressors, and other regressors that are dummy variables. The latter have the special property that the number of non-zero values is fixed, and does not increase with the sample size. We prove that the IV estimator of the coefficient vector for the dummy variables is inconsistent, while that for the other regressors is weakly consistent under standard assumptions. However, the usual estimator for the asymptotic covariance matrix of the I.V. estimator for all of the coefficients retains its usual consistency. The t-test statistics for the dummy variable coefficients are still asymptotically standard normal, despite the inconsistency of the associated IV coefficient estimator. These results extend the earlier results of Hendry and Santos (2005), which relate to a fixed-regressor model, in which the dummy variables are non-zero for just a single observation, and OLS estimation is used.

Keywords: Dummy variables; indicator variables; instrumental variables; inconsistent estimator (search for similar items in EconPapers)
JEL-codes: C20 C26 C49 (search for similar items in EconPapers)
Pages: 16 pages
Date: 2011-05-04
New Economics Papers: this item is included in nep-ecm
Note: ISSN 1485-6441
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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Journal Article: On the Inconsistency of Instrumental Variables Estimators for the Coefficients of Certain Dummy Variables (2017)
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Persistent link: https://EconPapers.repec.org/RePEc:vic:vicewp:1106

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