We present a new condition on beliefs that guarantee the Bayesian implementability of all efficient social decision rules. We show that this condition is easy to verify and is both more interpretable and more general than the conditions that are found in the literature. We also study conditions...

We propose a comprehensive concept of oligopolistic equilibrium, allowing for a parametrized continuum of competition regimes, with each firm setting simultaneously both its price and its quantity and facing two constraints: one relative to its share ofthe market, the other relative to the size...