Liquidity Costs and Tiering in Large-Value Payment Systems

This paper develops and simulates a model of the emergence of networks in an interbank, RTGS payment system. A number of banks, faced with random streams of payment orders, choose whether to link directly to the payment system, or to use a correspondent bank. Settling payments directly on the system imposes liquidity costs which depend on the maximum liquidity overdraft incurred during the day. On the other hand, using a correspondent entails paying a flat fee, charged by the correspondent to recoup liquidity costs and to extract a profit. We specify a protocol whereby one bank in each period can revisit its choice whether to link directly to the system, or to become clients of other banks,…