On the Costs and Externalities of Intermediation.

Summary This thesis aims to determine and estimate the costs of intermediation and the externalities it generates. The advent of big data and AI is reshaping financial intermediation. Its benefits in terms of speed and costs are visible, but its impact remains poorly understood. I show that these technologies can increase financial frictions as well as the costs of financial intermediation. The 2008 financial crisis revealed the importance of liquidity problems. I provide a theoretical framework to understand the consequences of banking regulations on banks' liquidity problems. It reveals a new trade-off between capital and liquidity requirements. Finally, the costs and externalities of intermediation are studied in the context of international trade. For geographical reasons, some countries are dependent on having their goods transit through intermediary countries. This friction is analyzed theoretically and estimated empirically. Countries that appear to be unaffected (such as the United Kingdom) suffer from the price-distorting effects of this problem.