Fixed, Random, or Something in Between? – A Variant of HAUSMAN’s Specifi cation Test for Panel Data Estimators

This paper proposes a variant of the classical HAUSMAN specifi cation test commonly employed to decide whether the estimation of a random-eff ects model is a viable alternative to estimating fi xed eff ects. Whereas the classical test probes the equality of fi xed- and random eff ects, the proposed variant focuses on the equality of between-groups and fi xed-eff ects coeffi cients. While both test procedures lead to the same conclusions, the panel model specifi cation underlying our testing strategy facilitates the simultaneous estimation of the fi xed- and between-groups eff ects. As a consequence, we are able to examine both the equality of the whole range of coeffi cients as well as that of individual variables. The usefulness of the test is illustrated using a panel of household travel data for Germany.