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Negative variance estimates in panel data models

Laura Magazzini () and Giorgio Calzolari

No 15/2010, Working Papers from University of Verona, Department of Economics

Abstract: Negative values for estimated variances can arise in a panel data context. Empirical and theoretical literature dismisses the problem as not serious and a practical solution is to replace negative variances by its boundary value, i.e. zero. While this is not a concern when the individual variance components is "small" with respect to idiosyncratic variance component (making it indistinguishable from zero in practice), we claim that a negative estimated variance can also arise with a "large" individual variance component, when the orthogonality condition between the individual effects and regressors fails. Estimation problems are considered in the (feasible) generalized least squares and maximum likelihood frameworks.

Keywords: Panel data; random effect estimation; negative variances; maximum likelihood (search for similar items in EconPapers)
JEL-codes: C23 (search for similar items in EconPapers)
Date: 2010-10
New Economics Papers: this item is included in nep-ecm
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