(19)In order to provide competent authorities with a consistent and accurate overview of the rating systems that the institution has been using as well as the improvement of the rating systems over time, it is necessary for competent authorities to assess the completeness of the register of the current and historical versions of rating systems used by the institution (‘register of rating systems’). Having regard to the fact that the requirements of the experience test relate to the preceding three years from the time of consideration of an application for approval of an internal model, and that the competent authorities are to carry out an overall review of the internal model on a regular basis, and at least every three years, it is appropriate for competent authorities to verify that such a register of rating systems covers at least the versions of the internal models used by the institution over the three preceding years.