In each period, bankjmaximizes its profits choosing prices and quantities:maxRLj;t;bj;tbj;tRLj;tdj;tRt;subject to the demand schedule in (8) and to the production function in (10). The first order con-dition for this problem implies that the optimal lending rate applied by banks is a positive con-stant gross markup (M) over the marginal cost:RLt(j) =zz1Rt=MRt:(11)Note that, together with consumers’ optimality conditions, equation (11) determines the equilib-rium of the economy. That is, once the lending rate has been set by banks, households make theirconsumption (and, therefore, borrowing) decisions. The market clearing in the loan market closesthe model.We also assume that the banking sector displays short-run interest rate stickiness. In particular,we assume that banks cannot immediately adjust their lending rates in response to macroeco-nomic developments. The presence of interest rate stickiness in the banking sector can be justi-fied by the presence of adjustment costs of and monopolistic power. For example, Hannan andBerger (1991) show that, in the presence of fixed adjustment costs, banks re-set their lendingrates only if the costs of changing the interest rate are lower than the costs of maintaining a non-equilibrium rate (see also Neumark and Sharpe, 1992). Empirically, it is a well documented factthat the adjustment of banks lending rates to changes in the risk-free rate is only partial and het-erogeneous, in particular in the short run. For example, Kwapil and Scharler (2010) show that in-terest rate pass-through of consumer loans in the U.S. can be as low as 0.3, implying that interestrates charged on consumer loans are smoothed heavily by banks. For tractability, we implementinterest rate stickiness by means of a simple one-period real rigidity —while we assume that inthe long-run interest rates are fully flexible.In particular we assume that, if the risk-free interest rate is hit by a temporary shock (u) in period0, only a fractionmof the banks can reset their rates, whereas the remaining 1mbanks cannot.This entails that, following a shock to the risk free interest rate, theaggregatelending rate will bein general different from the one desired by banks: remembering that consumers are price takersand that their loans demand depends on theaverageinterest rate in the economy, this friction willlead to a distortion in the competitive equilibrium and will create the policy scope for restoringefficiency. Moreover, given that the incomplete pass-through of changes in the risk-free rate onlending rates is a realistic assumption only in the short run, we assume that from period 1 interestrates are again fully flexible.