If the monetary policy objective and the supervisory objective are distinctly defined and separate instruments are assigned to each of them, then a single institution could take the interdependencies better into account than separate authorities.
Thus, in terms of our interaction with the market, it may be surprising but it is nonetheless true that membership of monetary union has actually brought the Central Bank in contact with a wider range of domestic counterparties than was the case before 1999. The Eurosystem is also responsible for the smooth operation of payment systems.