(23)Credit rating agencies should use rating methodologies that are rigorous, systematic, continuous and subject to validation including by appropriate historical experience and back-testing. Such a requirement should not, however, provide grounds for interference with the content of credit ratings and methodologies by the competent authorities and the Member States. Similarly, the requirement that credit rating agencies review credit ratings at least annually should not compromise the obligation on credit rating agencies to monitor credit ratings on a continuous basis and review credit ratings as necessary. Those requirements should not be applied in such a way as to prevent new credit rating agencies from entering the market.