Testing the "Separability" Condition in Two-Stage Nonparametric Models of Production
Cinzia Daraio (),
Leopold Simar () and
Paul W. Wilson ()
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Cinzia Daraio: Department of Computer, Control and Management Engineering Antonio Ruberti (DIAG), University of Rome La Sapienza, Rome, Italy
Paul W. Wilson: Department of Economics and School of Computing, Clemson University, Clemson, SC 29634
No 2015-08, DIAG Technical Reports from Department of Computer, Control and Management Engineering, Universita' degli Studi di Roma "La Sapienza"
Simar and Wilson (J. Econometrics, 2007) provided a statistical model that can rationalize two-stage estimation of technical efficiency in nonparametric settings. Two-stage estimation has been widely used, but requires a strong assumption: the second-stage environmental variables cannot affect the support of the input and output variables in the first stage. In this paper, we provide a fully nonparametric test of this assumption. The test relies on new central limit theorem (CLT) results for unconditional efficiency estimators developed by Kneip et al. (Econometric Theory, 2015a) and new CLTs for conditional efficiency estimators developed in this paper. The test can be implemented relying on either asymptotic normality of the test statistics or using bootstrap methods to obtain critical values. Our simulation results indicate that our tests perform well both in terms of size and power. We present a real-world empirical example by updating the analysis performed by Aly et al. (R. E. Stat., 1990) on U.S. commercial banks; our tests easily reject the assumption required for two-stage estimation, calling into question results that appear in hundreds of papers that have been published in recent years.
Keywords: technical efficiency; conditional efficiency; two-stage estimation; bootstrap; separability; data envelopment analysis (DEA); free-disposal hull (FDH). (search for similar items in EconPapers)
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Working Paper: Testing the "separability" condition in two-stage nonparametric models of production (2015)
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