A minimal requirement on allocative efficiency in the social sciences is Pareto optimality. In this paper, we identify a close structural connection between Pareto optimality and perfection that has various algorithmic consequences for coalition formation. Based on this insight, we formulate the...

In various models of matching markets, substitutable preferences constitute the largest domain for which stable matchings are guaranteed to exist. Recently, Hatfield et al. (2012) have proposed an efficient algorithm to test substitutability of strict preferences. In this note we show how the...