Comment: 10 pages, 2 figures. Version 2: removed simulation and discussion, added section 2.1 "equivalent statements", shortened proofsI relate bipartite graph matchings to stable matchings. I prove a necessary and sufficient condition for the existence of a saturating stable matching, where every agent on one side is matched, for all possible preferences. I extend my analysis to perfect stable matchings, where every agent on both sides is matched.