(15)The requirements for estimating LGDs and CFs in Regulation (EU) No 575/2013 require institutions to document the design and operational details of their rating systems, including the design of their processes for identifying economic downturns, and to retain evidence to show compliance with the estimation requirements in that Regulation. Regulation (EU) No 575/2013 further requires institutions to review their LGD and CF estimates and any input data required to make these estimates when new information comes to light and, in any event, at least annually.