Politique monétaire et concurrence bancaire

This paper focuses on the monetary policy channels in an imperfect competition framework of the banking sector. It emphasizes the relationship between the commercial banks rate and the lending rate of the central bank. The framework of imperfect competition is provided by the Salop [1979] model of horizontal differentiation which is applied to the banking sector and which is extended, to take account of the loan demand function elasticity. We shown that when the loan demand function is sufficiently convex (log convex), the banking sector exacerbates surprises in the monetary policy. This result is relevant for the efficiency of the monetary policy and for the behavior of the central bank when facing shocks of the loan demand function. Then, we study what should be the optimal implementation of the monetary policy when the central bank is concerned with both the price stability and the financial stability of the banking sector. In the model, the price stability is looked through an quantitative objective for the loans provided by the banking sector. We show that the trade-off between financial stability and price stability induces violent surprises in the monetary policy with respect to the volatility of the loan demand function.