First Author:   Myrna Wooders Department of Economics, University of Warwick M.Wooders@warwick.ac.uk         http://www.warwick.ac.uk/fac/soc/Economics/wooders/ Second Author: Hugo van den Berg Department of Mathematics, University of Warwick hugo@mail.maths.warwick.ac.uk         http://www.maths.warwick.ac.uk/staff/hugo.html