In the transmission of monetary policy, banks’ administered interest rates set by their market power may not coordinate well with the policy intention. In this study, we examine the effect of banks’ net interest rate spread (NIS) on real economic growth in response to changes in the benchmark interest rate in Korea. We find that the market power component of the NIS interacting with the benchmark rate significantly affects the prediction of future economic growth, especially under loosening monetary policy. Our findings indicate that when the policy interest rate decreases to boost the economy, monopolistic banks widen the NIS by sluggishly adjusting the lending rate, which dampens the growth effect. This misalignment remains consistent when we focus on the subperiod after the 2008 financial crisis and use alternative measures for our main variables.

在货币政策传导中，银行通过市场力量设定的管理利率可能与政策意图不能很好地协调。在本研究中，我们研究了银行净利差（NIS）对韩国基准利率变化对实际经济增长的影响。我们发现，NIS 的市场力量成分与基准利率相互作用显着影响对未来经济增长的预测，特别是在宽松的货币政策下。我们的研究结果表明，当政策利率下降以提振经济时，垄断银行通过缓慢调整贷款利率来扩大净利差，从而抑制增长效应。