[1] Univ Groningen, Dept Mkt, Fac Econ & Business, NL-9700 AV Groningen, Netherlands
[2] Tech Univ Darmstadt, Dept Informat Syst Elect Markets, Darmstadt, Germany
[3] Goethe Univ Frankfurt, Dept Mkt, Fac Business & Econ, Frankfurt, Germany
[4] BASF AG, D-6700 Ludwigshafen, Germany