%A Ennio Bilancini
%A Leonardo Boncinelli
%N 1
%L eprints3884
%V 108
%R doi:10.1016/j.econlet.2010.03.005
%D 2010
%J Economics Letters
%T Preferences and normal goods: An easy-to-check necessary and sufficient condition
%P 13-15
%K Normal goods; Bordered Hessian
%I Elsevier
%X We provide a necessary and sufficient condition for goods to be normal when utility functions are differentiable and strongly quasi-concave. Our condition is equivalent to the condition proposed by Alarie et al. (1990), but it is easier to check: it only requires to compute the minors associated with the border column (or row) of the bordered Hessian matrix of the utility function.