Atomic Leontievian Walrasian traders are always Cournotian

Abstract We consider a bilateral oligopoly version of the Shapley window model with large traders, represented as atoms, and small traders, represented by an atomless part. For this model, we show that, when atoms have Leontievian utility functions, any Walras allocation is a Cournot-Nash allocation. This result, together with the main theorem proved in Busetto et al. (2020), implies the equivalence between the set of Cournot-Nash allocations and the set of Walras allocations.