Thijs ten Raa Tilburg University   Tilburg University Box 90153 Tilburg, Brabant NL-5000 LE the Netherlands   tenRaa@UvT.nl   http://center.UvT.nl/staff/raa   Biographical Sketch: See web site.       JEL Areas: O3 : Technological Change; Research and Development: General D0 : Microeconomics: General