摘要：The effective federal funds rate is determined in acompetitive interbank market, while the target federalfunds rate represents a policy variable. This paper proposesa theory of the determination of the effective funds rate.According to the main result, the latter is a Lagrange multiplierthat vanishes if excess reserves emerge. This is exactlywhat happened in the United States in September 2008.In such a situation, paying interest on reserves does notchange bank incentives
关键词：Federal funds rate; term structure of interest;rates; excess reserves; money multiplier; zero lower bound
