A theory of strategic intermediation and endogenous liquidity

Market liquidity is typically characterized by a number of ad hoc metrics, such as depth (or market impact), volume, intermediation costs (such as breadth) etc. No general coherent denition seems to exist, and few attempts have been made to justify the existing metrics on welfare grounds. In this paper we propose a welfare-based denition of liquidity and characterize its relationship with the usual proxies. The model on which the welfare analysis rests is an equilibrium model with multiple assets and restricted investor participation. Strategic intermediaries pursue prot opportunities by providing intermedia- tion services (i.e. \liquidity") in exchange for an endogenous fee. Our model is well suited to study the contagion-like eects of liquidity shocks. We also consider the case in which intermediaries can optimally design securities.