This paper was produced in the framework of MICRO-DYN (www.micro-dyn.eu ), an international research project funded by the EU Sixth Framework Programme (www.cordis.lu ) with socio-economic sciences and humanities (http://ec.europa.eu/research/social-sciences/index_en.html ). This publication reflects only the author's views, the European Community is not liable for any use that may be made of the information contained therein. !" !! #!$ " "%# &! !$ &"’&! %’ %( )# *& +# , -