[1] Justus Liebig Univ Giessen, Inst Geog, Senckenbergstr 1, D-35390 Giessen, Germany
[2] Univ Bremen, Inst Labour & Econ, Bibliothekstr 1, D-28359 Bremen, Germany
[3] Stat Bundesamt, Gustav Stresemann Bing 11, D-65189 Wiesbaden, Germany
[4] Umwelt Campus Birkenfeld IfaS, Hsch Trier, Postfach 1380, D-55761 Birkenfeld, Germany