The interest rate spread, which is the difference between the bank’s earnings from loaned funds and its cost of funds is influenced by non-interest expense, prudential and reserve requirements, market structure, inflation, credit risk and profit expectation of banks, among others.
Also, in the longer run, what is crucial for the real income of the savers is the state of the economy. A central bank has no influence on factors which determine the structural strength of an economy and thus the real, or inflation-adjusted, interest rates. Standard: That’s not much help to savers today.