[We explore the implications of financial system design for financial innovation. We begin with assumptions about the investment opportunities of firms, their observable attributes, and the roles of commercial banks, investment banks, and the financial market. We examine the borrower's choice between bank and financial market funding, the commercial bank's choice of monitoring capacity, and the investment bank's choice of whether to invest in financial innovation. Our main result is that financial innovation in a universal banking system is stochastically lower than innovation in a financial system in which commercial and investment banks are functionally separated.]

This article builds a theory of financial system architecture. We ask: what is a financial market, what is a bank, and what determines the economic role of each? Starting with basic assumptions about primitives–the types of agents and the nature of informational asymmetries–we provide a theory that explains which agents coalesce to form banks and which trade in the capital market. It is shown that borrowers of higher observable qualities access the financial market. Moreover, a financial system in its infancy will be bank-dominated, and increased financial market sophistication diminishes bank lending.

This article builds a theory of financial system architecture. We ask: what is a financial market, what is a bank, and what determines the economic role of each? Starting with basic assumptions about primitives—the types of agents and the nature of informational asymmetries—we provide a theory that explains which agents coalesce to form banks and which trade in the capital market. It is shown that borrowers of higher observable qualities access the financial market. Moreover, a financial system in its infancy will be bank-dominated, and increased financial market sophistication diminishes bank lending.