First Author:   Harry Haupt Department of Econometrics, University of Regensburg, Germany harald.haupt@wiwi.uni-r.de   University of Regensburg, Department of Econometrics Regensburg, 93040, Germany       http://uni-regensburg.de/Fakultaeten/WiWi/oberhofer/ Second Author: Walter Oberhofer Department of Econometrics, University of Regensburg, Germany walter.oberhofer@wiwi.uni-r.de