Testing for Separation in Agricultural Household Models and Unobservable Individual Effects: A Note
AbstractWhen market structure is complete, factor demands by households will be independent of their characteristics, and households will take their production decisions as if they were profit-maximizing firms. This observation constitutes the basis for one of the most popular empirical tests for complete markets, commonly known as the 'separation' hypothesis. In this paper, we show that all existing tests for separation using panel data are potentially biased towards rejecting the null-hypothesis of complete markets, because of the failure to adequately control for unobservable individual effects. Since the variable on which the test for separation is based cannot be identified in most panel datasets following the usual covariance transformations, and is likely to be correlated with the individual effect, neither the within nor the variance-components procedures are able to solve the problem. We show that the Hausman-Taylor (1981) estimator, in which the impact of covariates that are invariant along one dimension of a panel can be identified through the use of covariance transformations of other included variables that are orthogonal to the individual effects as instruments, provides a simple solution. We furnish an empirical illustration in which separation —and thus the null of complete markets— is strongly rejected using the standard approach, but is not rejected once correlated unobservable individual effects are controlled for using the Hausman-Taylor instrument set.
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Bibliographic InfoPaper provided by EconWPA in its series Microeconomics with number 0510007.
Length: 11 pages
Date of creation: 11 Oct 2005
Date of revision:
Note: Type of Document - pdf; pages: 11
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Panel data; individual effects; household models; testing for incomplete markets; development microeconomics; Tunisia;
Other versions of this item:
- Jean-Louis ARCAND & Béatrice D'HOMBRES, 2002. "Testing for Separation in Agricultural Household Models and Unobservable Individual Effects: A Note," Working Papers 200225, CERDI.
- D1 - Microeconomics - - Household Behavior
- D2 - Microeconomics - - Production and Organizations
- D3 - Microeconomics - - Distribution
- D4 - Microeconomics - - Market Structure and Pricing
This paper has been announced in the following NEP Reports:
- NEP-AGR-2005-10-15 (Agricultural Economics)
- NEP-ALL-2005-10-15 (All new papers)
- NEP-CWA-2005-10-15 (Central & Western Asia)
- NEP-ECM-2005-10-15 (Econometrics)
- NEP-MIC-2005-10-15 (Microeconomics)
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