What's different among banks?

Based on commercial paper being a nearly perfect substitute for certificates of deposits (CDs) and CD reserve requirements creating a higher cost of funds for banks, Fama shows that the banking industry must have some monopoly power relative to other financial institutions. His analysis does not resolve whether this monopoly power is vested in banks collectively, vis-à-vis other financial institutions, or if the monopoly power extends to the level of individual banks. Using an event study framework to examine the elimination of a reserve requirement, we find significant evidence of monopoly power at the level of individual banks.