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5.2 Review of Rating System Developments

الرقم: BCS 290 التاريخ (م): 2006/6/12 | التاريخ (هـ): 1427/5/16 الحالة: No longer applicable
5.2.1The first analytical support for the validity of a bank’s rating system is review of rating system developments, in particular analyzing its design and construction. The aim of the review is to assess whether the rating system could be expected to work reasonably if it is implemented as designed. Such review should be revisited whenever the bank makes a change to its rating system. As the rating system is likely to change over time as the bank learns about the effectiveness of the system, the review is likely to be an ongoing part of the process. The particular steps taken in the review depends on the type of rating system.
 
5.2.2Regarding a model-based rating system, the review of rating system developments should include information on the logic that supports the model and an analysis of the statistical model-building techniques. The review should also include empirical evidence on how well the ratings might have worked in the past, as such models are chosen to maximize the fit to outcomes in the development sample. In addition, statistical models should be supported by evidence that they work well outside the development sample. Use of out-of-time and out-of-sample performance tests is a good model-building practice to ensure that the model is not merely a statistical quirk of the particular data set used to build the model. Where a bank uses scoring systems for assigning credit ratings, it should demonstrate that those systems have adequate discriminating power.
 
5.2.3Regarding an expert judgment-based rating system, the review of rating system developments requires asking two groups of raters how they would rate credits based on the rating definitions, processes and criteria for assigning exposures to grades within the rating system (see sections 4 and 5 of the “Minimum Requirements for Internal Rating Systems under IRB Approach” on requirements for rating criteria and processes). These two sets of rating results could then be compared to determine whether the ratings were consistent. Conducting such tests would help identify any factors, which may lead to different or inconsistent ratings. While some differences and inconsistencies may arise from the exercise of judgment, those findings should be considered for the development of the rating system.
 
5.2.4Where an expert judgment-based rating system which employs quantitative guidelines or model results as inputs, the review of the rating system that features guidance values of financial ratios or scores of a scoring model might include a description of the logic and evidence relating the values of the ratios or scores to past default and loss outcomes.