Research Methods for Validating Credit Ratings and Default Models
Summary
The document answers a question about how to assess the historical quality of credit ratings from agencies such as Fitch, S&P, and Moody’s. Its response points readers to research on rating validation, corporate bond rating performance, and the relationship between competition and ratings. It also lists work on validating probability-of-default models, including approaches based on changes in firm credit quality, stress testing, and Bayesian assessment of default distributions.
The material is primarily a bibliography rather than a detailed tutorial: it names academic papers, industry research, and a regulatory examination as starting points. It suggests that rating quality can be studied through model validation and observed default outcomes, while the cited topics indicate different ways to frame the analysis. No results, datasets, or step-by-step methodology are provided in the document, so readers must consult the references to compare methods and evidence. The examples span corporate ratings and probability-of-default models; they do not establish that any one validation procedure applies to every agency, market, or rating use case.
Key ideas
- Credit rating quality has been examined in academic, industry, and regulatory research.
- Validation studies can assess probability-of-default models against observed credit outcomes.
- The cited methods include stress testing, Bayesian validation, and analysis of shocks to firm credit quality.
- Corporate bond rating performance and agency competition are additional research topics.
- The document provides references rather than summarizing findings or prescribing a single validation method.
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Full text
# Assessing Credit Rating Agencies # Assessing Credit Rating Agencies Has there been any historical evaluation of the quality of credit ratings provided by agencies such as Fitch, S&P, and Moody's? Are there any academic resources available on this topic? I have checked Google Scholar, but could not find much. I'm curious to learn more about this topic, including the methodologies that can be used to test the accuracy of these credit ratings. ## Answer by Dimitri Vulis (score 4, accepted) https://quant.stackexchange.com/a/74695 There are many papers. Here are some random examples: Many of the papers under https://www.michaeljacobsjr.com/research-papers/ http://dx.doi.org/10.2139/ssrn.1466710 Ralf Elsas, Sabine Mielert. Rating Validation Based on Shocks to Firms’ Credit Quality http://dx.doi.org/10.2139/ssrn.2521216 Sean Flynn, Andra Ghent. Competition and Credit Ratings After the Fall. https://dx.doi.org/10.1016/j.jbankfin.2008.11.007 Lydian Medema, Ruud Koning, Robert Lensink A practical approach to validating a PD model. http://dx.doi.org/10.21314/JRMV.2021.009 Mark Rubtsov. Backtesting of a probability of default model in the point-in-time–through-the-cycle context. https://dx.doi.org/10.1016/j.irfa.2016.06.007 Fábio Yasuhiro Tsukahara, Herbert Kimura, Vinicius Amorim Sobreiro, Juan Carlos Arismendi Zambrano. Validation of default probability models: A stress testing approach. http://dx.doi.org/10.21314/JRMV.2007.003 Douglas Dwyer. The distribution of defaults and Bayesian model validation. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=996025 Richard Cantor, Christopher Mann. Measuring the Performance of Corporate Bond Ratings. Moody's Special Comment. https://www.spglobal.com/marketintelligence/en/news-insights/research/demystifying-credit-risk-models-backtesting-and-recalibration Credit Analytics Statistical Models’ Backtesting and Recalibration: A Primer https://www.wsj.com/articles/inflated-bond-ratings-helped-spur-the-financial-crisis-theyre-back-11565194951 Cezary Podkul, Gunjan Banerji. Inflated Bond Ratings Helped Spur the Financial Crisis. They’re Back. https://www.sec.gov/news/studies/2008/craexamination070808.pdf
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