Differences of opinion and selection bias in the credit rating industry

Many regulations use private sector credit ratings to determine investment prohibitions and capital requirements for institutional portfolio investments. These regulations implicitly assume that different agencies have equivalent rating scales, despite the fact that some agencies assign systematically higher ratings than others. We assess the appropriateness of these regulatory practices by testing whether observed rating differences reflect different rating scales or simply result from sample selection bias. Our analysis reveals only limited evidence of selection bias. We also ask what types of firms of firms are most likely to seek ratings from the agencies with higher rating scales. Our analysis uncovers no evidence that firms seek ratings from these agencies to clear specific regulatory hurdles or to reduce ex ante uncertainty about default risk.     

The credit rating process and estimation of transition probabilities: A Bayesian approach

The Basel II Accord requires banks to establish rigorous statistical procedures for the estimation and validation of default and ratings transition probabilities. This raises great technical challenges when sufficient default data are not available, as is the case for low default portfolios. We develop a new model that describes the typical internal credit rating process used by banks. The model captures patterns of obligor heterogeneity and ratings migration dependence through unobserved systematic macroeconomic shocks. We describe a Bayesian hierarchical framework for model calibration from historical rating transition data, and show how the predictive performance of the model can be assessed, even with sparse event data. Finally, we analyze a rating transition data set from Standard and Poor's during 1981–2007. Our results have implications for the current Basel II policy debate on the magnitude of default probabilities assigned to low risk assets.     

Initial credit ratings and earnings management

Credit rating agencies assert that they rely on financial information provided by issuers and that they value rating stability as well as accuracy. In an environment where rating agencies depend on issuer-reported information and are reluctant to adjust ratings promptly, managers of issuing firms can utilize the discretion afforded by GAAP to obtain the most favorable credit ratings. Consistent with our expectations, we find that current accruals are unusually positive and high around initial credit ratings. The increase in abnormally high accruals leading up to the initial credit rating year is followed by a reversal in the subsequent years. Multivariate regression analyses suggest that accounting accruals, abnormal current accruals in particular, are significantly positively related to initial credit ratings after controlling for several issue- and issuer-related characteristics indicative of default risk. Our results are robust to additional tests that account for endogeneity between credit ratings and earnings management, adjust for performance, and account for firms issuing debt and equity simultaneously.     

How rating agencies achieve rating stability

Surveys on the use of agency credit ratings reveal that some investors believe that rating agencies are relatively slow in adjusting their ratings. A well-accepted explanation for this perception on the timeliness of ratings is the through-the-cycle methodology that agencies use. According to Moody’s, through-the-cycle ratings are stable because they are intended to measure default risk over long investment horizons, and because they are changed only when agencies are confident that observed changes in a company’s risk profile are likely to be permanent. To verify this explanation, we quantify the impact of the long-term default horizon and the prudent migration policy on rating stability from the perspective of an investor – with no desire for rating stability. This is done by benchmarking agency ratings with a financial ratio-based (credit-scoring) agency-rating prediction model and (credit-scoring) default-prediction models of various time horizons. We also examine rating-migration practices. The final result is a better quantitative understanding of the through-the-cycle methodology.By varying the time horizon in the estimation of default-prediction models, we search for a best match with the agency-rating prediction model. Consistent with the agencies’ stated objectives, we conclude that agency ratings are focused on the long term. In contrast to one-year default prediction models, agency ratings place less weight on short-term indicators of credit quality.We also demonstrate that the focus of agencies on long investment horizons explains only part of the relative stability of agency ratings. The other aspect of through-the-cycle methodology – agency-rating migration policy – is an even more important factor underlying the stability of agency ratings. We find that rating migrations are triggered when the difference between the actual agency rating and the model predicted rating exceeds a certain threshold level. When rating migrations are triggered, agencies adjust their ratings only partially, consistent with the known serial dependency of agency-rating migrations.     

Financial statement comparability and credit risk

Prior research shows that firms’ financial statement comparability improves the accuracy of market participants’ valuation judgments and thus may reduce firms’ costs of capital. Distinct from prior research focusing on the equity market, we develop measures of comparability relevant to debt market participants based on the within-industry variability of Moody’s adjustments to reported accounting numbers for the purposes of credit rating. We examine two sets of adjustments: (1) to the interest coverage ratio and (2) to non-recurring income items. We validate these comparability measures by providing evidence that greater comparability is associated with lower frequency and magnitude of split ratings by credit rating agencies. We predict and find that greater comparability is associated with (1) lower estimated bid-ask spreads for traded bonds, (2) lower credit spreads for both bonds and five-year credit default swaps, and (3) a steeper one- to five-year credit default swap term structure. Our results are consistent with financial statement comparability reducing debt market participants’ uncertainty about and pricing of firms’ credit risk.     

The Role of Default Risk in Determining the Market Reaction to Debt Announcements

The stock price reaction to straight debt announcements is examined by differentiating firms on the basis of any subsequent change in their overall default risk. Results indicate that firms that will within six months of straight debt announcements undergo debt rating downgrades experience significant negative abnormal stock returns at the time of the new debt announcements, while firms with bond ratings that are later upgraded exhibit significant positive abnormal returns. Multiple regression analysis shows these results to be robust to the influence of filing size, tax shield effects, relative pre-announcement long-term debt levels, and subordination effects.     

Political similarities in credit ratings

We investigate whether political similarities between credit rating agencies (CRAs) and bond issuers impact credit rating quality. We find that a higher degree of similarity of political affiliation leads to a decrease in timeliness and accuracy of downgrades prior to default events. Our finding supports the notion that CRAs tend to maintain/assign preferential ratings to politically similar firms via delaying negative signals as favourable rating activities. We further show that these politically similar firms tend to increase the proportion of donations to their favoured party following favourable credit ratings. Interestingly, this result is confined to Republican-leaning firms. The results indicate that CRAs successfully use biased credit ratings as an indirect channel of political party support. Our findings support the political similarities in credit ratings hypothesis.     

A simple continuous measure of credit risk

This paper introduces a simple parameterization for the risk-neutral default probability distributions for risky firms that are easily computed from quoted bond prices. The corresponding expected times to default have a particularly simple form and are proposed as a measure for credit risk. Being continuous in nature, times to default provide a much finer measure of risk than those provided by ratings agencies. Comparison with the ratings provided by Moody's and the distance to default measures calculated using the Merton [Merton, R. (1974). On the pricing of corporate debt: the risk structure of interest rates. Journal of Finance, 2(2), 449-470] model shows that the highest rank correlation is found between the proposed time to default measure and Moody's ratings.     

Structural Shifts in Credit Rating Standards

I examine the time‐series variation in corporate credit rating standards from 1985 to 2007. A divergent pattern exists between investment‐grade and speculative‐grade rating standards from 1985 to 2002 as investment‐grade standards tighten and speculative‐grade loosen. In 2002, a structural shift occurs toward more stringent ratings. Holding characteristics constant, firms experience a drop of 1.5 notches in ratings due to tightened standards from 2002 to 2007. Credit spread tests suggest that the variation in standards is not completely due to changes in the economic climate. Rating standards affect credit spreads. Loose ratings are associated with higher default rates.     

Firm heterogeneity and credit risk diversification

This paper examines the impact of neglected heterogeneity on credit risk. We show that neglecting heterogeneity in firm returns and/or default thresholds leads to underestimation of expected losses (EL), and its effect on portfolio risk is ambiguous. Once EL is controlled for, the impact of neglecting parameter heterogeneity is complex and depends on the source and degree of heterogeneity. We show that ignoring differences in default thresholds results in overestimation of risk, while ignoring differences in return correlations yields ambiguous results. Our empirical application, designed to be typical and representative, combines both and shows that neglected heterogeneity results in overestimation of risk. Using a portfolio of U.S. firms we illustrate that heterogeneity in the default threshold or probability of default, measured for instance by a credit rating, is of first order importance in affecting the shape of the loss distribution: including ratings heterogeneity alone results in a 20% drop in loss volatility and a 40% drop in 99.9% VaR, the level to which the risk weights of the New Basel Accord are calibrated.     

Constant Proportion Debt Obligations (CPDOs): modeling and risk analysis

Constant Proportion Debt Obligations (CPDOs) are structured credit derivatives that generate high coupon payments by dynamically leveraging a position in an underlying portfolio of investment-grade index default swaps. CPDO coupons and principal notes received high initial credit ratings from the major rating agencies, based on complex models for the joint transition of ratings and spreads for all names in the underlying portfolio. We propose a parsimonious model for analysing the performance of CPDO strategies using a top-down approach that captures the essential risk factors of the CPDO. Our approach allows us to compute default probabilities, loss distributions and other tail risk measures for the CPDO strategy and analyse the dependence of these risk measures on various parameters describing the risk factors. We find that the probability of the CPDO defaulting on its coupon payments can be made arbitrarily small—and thus the credit rating arbitrarily high—by increasing leverage, but the ratings obtained strongly depend on assumptions on the credit environment (high spread or low spread). More importantly, CPDO loss distributions are found to exhibit a wide range of tail risk measures inside a given rating category, suggesting that credit ratings are insufficient performance indicators for such complex leveraged strategies. A worst-case scenario analysis indicates that CPDO strategies have a high exposure to persistent spread-widening scenarios and that CPDO ratings are shown to be quite unstable during the lifetime of the strategy.     

“投资人付费”vs.“发行人付费”:谁的信用评级质量更高？

本文选择2011-2015年被中债资信覆盖的发债A股上市公司作为主要研究对象,比较了“投资人付费”与“发行人付费”模式下的评级质量高低。研究发现:(1)与“发行人付费”评级相比,采用“投资人付费”模式的中债资信所作评级显著更低。(2)与“发行人付费”评级相比,当采用“投资人付费”模式的中债资信所作评级越低时,发行人未来盈利能力越差、预期违约风险越高,投资者要求的风险补偿也越高,这表明“投资人付费”模式下的信用评级质量更高。(3)“发行人付费”模式的评级结果可以在一定程度上反映公司的内部私有信息,但由于同时存在独立性缺失问题,“发行人付费”模式的信用评级质量仍然不如“投资人付费”模式的信用评级质量,这说明独立性对于评级机构尤其重要。     

Good deeds earn chits? Evidence from philanthropic family controlled firms

This study examines whether charitable family controlled firms have lower default risk. Using Taiwan data that provide clear information about firms’ benevolent intention and avoid endogeneity issue of risk and charitable activities, we show that charitable family controlled firms have lower default risk, which is proxied by value-at-risk and expected shortfall measures. Our finding shows that charitable activities bring benefits of lower risk to shareholders. This study also provides various channels that can lower default risk for the charitable firms. That is, these firms appear to have higher credit ratings, engage less in earnings management, and have higher worker productivity. This study argues that the benevolent mindset of decision makers at firms help lower default risk.     

Do managers withhold bad news from credit rating agencies?

Research documents that managers, on average, withhold bad news and emphasize good news in their public disclosures. We ask whether the same is true in their private communications with credit rating agencies. We study how rating agencies anticipate and react to public information events as a function of their access to rated firms’ private information. We show that, in terms of ratings downgrades, rating agencies exhibit relatively more anticipation and less reaction to negative (compared to positive) public information events when they have more access to private information. Our results are strongest when firms are most optimistic in their public disclosures and are not due to rating agencies focusing their efforts on downside risk. Overall, we find consistent evidence that rated firms provide less optimistic information to rating agencies in their private communications and that this information is reflected in credit ratings.

     

Through-the-Cycle Ratings Versus Point-in-Time Ratings and Implications of the Mapping Between Both Rating Types

The two philosophies of ratings, one that includes cyclical effects and the other that doesn't, are mirrored by the two different rating types commonly known as point-in-time (pit) and through-the-cycle (ttc). Point-in-time ratings try to evaluate the current situation of a customer by taking into account both cyclical and permanent effects. In contrast, through the-cycle ratings focus mainly on the permanent component of default risk and are nearly independent from cyclical changes in the creditworthiness of a customer. In this paper we give a review of the characteristics of both rating types and examine whether these properties can actually be observed in practice. In this context we present the results of an analysis of Standard& Poor's rating data, which show that the ratings, though being through-the-cycle, still vary in accordance with the business cycle. Another concern of this paper is the wide spread practice to map 'external' through-the-cycle ratings to 'internal' point-in-time ratings, with the purpose to enrich or validate a financial institution's internal rating database. We show that in doing so financial institutions severely misspecify customers' risk profiles and under- or overestimate costs in connection with credit pricing or capitalization. We confirm our theoretical considerations by calculating pricing quantities when using one or the other rating information.     

What Drives the Consequences of Intentional Misstatements? Evidence from Rating Analysts’ Reactions

This paper aims to identify the mechanisms through which intentional misstatements adversely affect firms by analyzing rating analysts’ reaction to misstatements. In order to identify the mechanisms through which the misstatement affects firms’ credit ratings, we analyze the content of rating reports. Rating analysts are concerned about seven different mechanisms. They are most concerned about misstatement‐related violations of debt covenants that increase a firm's liquidity risk. We find that, subsequent to an intentional misstatement becoming publicly known, credit ratings of misreporting firms are adversely affected for up to seven years. The adverse impact of an intentional misstatement on a firm's credit rating is most pronounced in cases in which rating analysts mention concerns about misstatement‐related violations of covenants. Our results suggest that these covenant violations are the most severe mechanism through which misstatements adversely affect firms’ creditworthiness.     

债券评级机构变更——基于评级选购与评级迎合视角

本文以2008年至2017年的公司债券为样本,研究了发行人变更评级机构的影响,以此来解释评级市场上发行人频繁变更评级机构的现象。本文发现发行人变更评级机构后,其信用等级得到显著提升。发行人变更评级机构的行为对信用等级的影响在以下两种情形中更显著:一是当发行人所处行业或评级机构所在的评级市场竞争激烈时;二是当发行人主体评级位于AA信用等级的临界点时。进一步研究发现,考虑到评级机构变更与信用等级之间的交互影响,变更评级机构的发行人整体上可实现发债成本的降低。但该类发行人未来的违约风险增加、经营业绩下降。最后,本文发现债券发行规模较大以及非国有发行人更倾向于变更评级机构来提高信用等级。本文通过分析发行人更换信用评级机构的动机和后果,为监管部门构建以评级质量为导向的良性竞争环境提供借鉴参考。     

Rating friends: The effect of personal connections on credit ratings

Using a large sample of US public debt issues we show that personal connections between directors of issuing companies and rating agencies result in higher credit ratings. We estimate the average effect to be about one notch. Moreover, our tests indicate that issues by connected firms are 30% more likely to be rated A3. Results are robust to several alternative tests including additional controls for managerial traits, firm fixed effects, and propensity score matching. Furthermore, our tests on default rates and bond yields suggest that personal connections act as a mechanism to reduce asymmetric information between the rating agency and the issuer.     

Are Unsolicited Credit Ratings Lower? International Evidence From Bank Ratings

Abstract:   In recent years credit rating agencies have started rating firms who have not asked for a rating. Recipients of unsolicited ratings argue that the assigned ratings are too low and reflect a lack of comprehensive knowledge of the rated firms. We set out to examine these claims using a comprehensive and international sample of 1,060 bank ratings. Our results show that there is a significant difference in the distributions of ratings, and the shadow group has lower ratings. The results also indicate that banks that received shadow ratings are smaller and have weaker financial profiles than banks that have other ratings. This explains, in part, the lower ratings. In addition, we develop a model to explain bank ratings. The two‐step treatment effects model shows that bank size, profitability, asset quality, liquidity, and sovereign credit risk are important factors in determining bank ratings.     

Tranching and Rating

In this paper we analyse the source and magnitude of marketing gains from selling structured debt securities at yields that reflect only their credit ratings, or specifically at yields on equivalently rated corporate bonds. We distinguish between credit ratings that are based on probabilities of default and ratings that are based on expected default losses. We show that subdividing a bond issued against given collateral into subordinated tranches can yield significant profits under the hypothesised pricing system. Increasing the systematic risk or reducing the total risk of the bond collateral increases the profits further. The marketing gain is generally increasing in the number of tranches and decreasing in the rating of the lowest rated tranche.