Maximizing edge-ratio is NP-complete

This is the post-print verison of the Article. The official published version can be accessed from the link below - Copyright @ 2011 ElsevierGiven a graph G and a bipartition of its vertices, the edge-ratio is the minimum for both classes so defined of their number of internal edges divided by their number of cut edges. We prove that maximizing edge-ratio is NP-complete