Joachim Winter University of Mannheim   Mannheim Research Institute for the Economics of Aging (MEA) University of Mannheim Mannheim, 68131 Germany   winter@uni-mannheim.de   http://www.mea.uni-mannheim.de/winter       Primary Research Focus: applied econometrics; design of household surveys   JEL Areas: C8 : Data Collection and Data Estimation Methodology; Computer Programs: General D1 : Household Behavior: General