The relation between interest rate and profit rate: the role of bank profitability in an endogenous money framework

The relation between interest and profit rate is crucial, as it has a major impact on income distribution, and it is relevant for the interpretation of the functioning of the economic system. After reviewing the literature, I try to interpret this relation between rates using banking profitability as the keystone. The condition that the capital employed in the banking industry should receive a profit rate at least equal to the general profit rate, combined with a careful examination of the functioning of the banking sector, makes conceivable an endogenous determination of the interest rate. The bank interest rate on loans is the price of the "loan" commodity, given the production conditions of the banking sector, where the rate set by the central bank constitutes the price of an input of the banking industry. I also analyse the formation of the interest rate structure, taking as starting points the main refinancing rate set by the central bank and the normal profitability of bank capital, with the lending rate on bank loans being the upper margin and the deposit rate the lower margin of the interest rate corridor. The interest rates structure is thus determined by several elements, confirming Marx's idea of a heterogeneous determination of interest rates. Alternatively, it can be assumed that, as the banking industry is characterized by a high degree of monopoly, its profit rate is higher than the average for the rest of the economy. In Marxian terms this reflects contrast between financial capitalists and productive capitalists, where the high degree of monopoly of the banking sector becomes a weapon to capture a higher share of total profits.