The pernicious effects of contaminated data in risk management

Banks hold capital to guard against unexpected surges in losses and long freezes in financial markets. The minimum level of capital is set by banking regulators as a function of the banks’ own estimates of their risk exposures. As a result, a great challenge for both banks and regulators is to validate internal risk models. We show that a large fraction of US and international banks uses contaminated data when testing their models. In particular, most banks validate their market risk model using profit-and-loss (P/L) data that include fees and commissions and intraday trading revenues. This practice is inconsistent with the definition of the employed market risk measure. Using both bank data and simulations, we find that data contamination has dramatic implications for model validation and can lead to the acceptance of misspecified risk models. Moreover, our estimates suggest that the use of contaminated data can significantly reduce (market-risk induced) regulatory capital.     

Integrated models of capital adequacy – Why banks are undercapitalised

With the majority of large UK and many US banks collapsing or being forced to raise capital over the 2007–9 period, blaming bankers may be satisfying but is patently insufficient; Basel II and Federal oversight frameworks also deserve criticism. We propose that the current methodological void at the heart of Basel II, Pillar 2 is filled with the recommendation that banks develop fully-integrated models for economic capital that relate asset values to fundamental drivers of risk in the economy to capture systematic effects and inter-asset dependencies in a way that crude correlation assumptions do not. We implement a fully-integrated risk analysis based on the balance sheet of a composite European bank using an economic-scenario generation model calibrated to conditions at the end of 2007. Our results suggest that the more modular, correlation-based approaches to economic capital that currently dominate practice could have led to an undercapitalisation of banks, a result that is clearly of interest given subsequent events. The introduction of integrated economic-scenario-based models in future can improve capital adequacy, enhance Pillar 2’s application and rejuvenate the relevance of the Basel regulatory framework.     

Private equity and regulatory capital

Regulatory capital requirements for European banks have been put forward in the Basel II Capital Framework and subsequently in the capital requirements directive (CRD) of the EU. We provide a detailed discussion of the capital requirements for private equity investments under different approaches. For the internal model approach we present a structural model that we calibrate to a proprietary dataset. We modify the standard Merton structural model to make it applicable in practice and to capture stylized facts of private equity investments. We also implement the early default feature with a fast simulation algorithm. Our results support capital requirements lower than in Basel II, but not as low as in CRD, thereby giving adverse incentives to banks for using advanced risk models. A sensitivity analysis shows that this finding is robust to parameter uncertainty and stress scenarios.     

Optimal portfolios with minimum capital requirements

We propose a novel approach to active risk management based on the recent Basel II regulations to obtain optimal portfolios with minimum capital requirements. In order to avoid regulatory penalties due to an excessive number of Value-at-Risk (VaR) violations, capital requirements are minimized subject to a given number of violations over the previous trading year. Capital requirements are based on the recent Basel II amendments to account for the ‘stressed’ VaR, that is, the downside risk of the portfolio under extreme adverse market conditions. An empirical application for two portfolios involving different types of assets and alternative stress scenarios demonstrates that the proposed approach delivers an improved balance between capital requirement levels and the number of VaR exceedances. Furthermore, the risk-adjusted performance of the proposed approach is superior to that of minimum-VaR and minimum-stressed VaR portfolios.     

Capital-based regulation,portfolio risk and capital determination: Empirical evidence from the US property–liability insurers

This paper examines the impact of capital-based regulation on the insurer’s risk and capital adjustments in the US property–liability insurance industry. We conduct the three-stage least squares (3SLS) procedure to estimate a simultaneous equations model. The key finding is that undercapitalized insurers increase capital to avoid regulatory costs and take more risks to generate higher returns. We also investigate firm characteristics that determine the insurer’s capital structure. The results indicate that insurers appear to rely heavily on retained earnings to make up their capital shortage and insurers with greater growth opportunity may hold high levels of capital to control for agency problems. Robustness tests with an alternative risk measure and subsamples present consistent results.     

Common risk factors in bank stocks

This paper provides evidence on the risk factors that are priced in bank equities. Alternative empirical models with precedent in the nonfinancial asset pricing literature are tested, including the single-factor CAPM, three-factor Fama–French model, and ICAPM. Our empirical results indicate that an unconditional two-factor ICAPM model that includes the stock market excess return and shocks to the slope of the yield curve is useful in explaining the cross-section of bank stock returns. However, we find no evidence that firm specific factors such as size and book-to-market ratios are priced in bank stock returns. These results have a number of important implications for the estimation of the banks’ cost of capital as well as regulatory initiatives to utilize market discipline to evaluate bank risk under Basel II.     

Stress testing credit risk: The Great Depression scenario

By employing Moody’s corporate default and rating transition data spanning the last 90 years we explore how much capital banks should hold against their corporate loan portfolios to withstand historical stress scenarios. Specifically, we will focus on the worst case scenario over the observation period, the Great Depression. We find that migration risk and the length of the investment horizon are critical factors when determining bank capital needs in a crisis. We show that capital may need to rise more than three times when the horizon is increased from 1 year, as required by current and future regulation, to 3 years. Increases are still important but of a lower magnitude when migration risk is introduced in the analysis. Further, we find that the new bank capital requirements under the so-called Basel 3 agreement would enable banks to absorb Great Depression-style losses. But, such losses would dent regulatory capital considerably and far beyond the capital buffers that have been proposed to ensure that banks survive crisis periods without government support.     

Capital management in mutual financial institutions

Capital management by mutual financial institutions (such as credit unions) provides a valuable testing ground for assessing the impact of capital regulation and theories of managerial behaviour in financial institutions. Limited access to external equity capital means that capital accumulation must be met primarily by reliance on retained earnings. To deal with shocks to the capital position and avoid breaching regulatory requirements, managers will aim to have a buffer of capital in excess of the regulatory minimum. Moreover, mutual governance arrangements and an absence of capital market discipline mean that managers have discretion to set target capital ratios which differ significantly from industry averages. This paper develops a formal model of capital management and risk management in mutual financial institutions such as credit unions which reflects these industry characteristics. The model is tested using data from larger credit unions in Australia, which have been subject to the Basel Accord Risk Weighted Capital Requirements since 1993. The data supports the hypothesis that credit unions manage their capital position by setting a short term target profit rate (return on assets) which is positively related to asset growth and which is aimed at gradually removing discrepancies between the actual and desired capital ratio. Desired capital ratios vary significantly across credit unions. There is little evidence of short run adjustments to the risk of the asset portfolio to achieve a desired capital position.     

Ratings based capital adequacy for securitizations

This paper develops a framework to measure the exposure to systematic risk for pools of asset securitizations and measures empirically whether current ratings-based rules for regulatory capital of securitizations under Basel II and Basel III reflect this exposure. The analysis is based on a comprehensive US dataset on asset securitizations for the time period between 2000 and 2008. We find that the shortfall of regulatory capital during the Global Financial Crisis is strongly related to ratings. In particular, we empirically show that insufficient capital is allocated to tranches with the highest rating. These tranches account for the greatest part of the total issuance volumes. Furthermore, this paper is the first to calibrate risk weights which account for systematic risk and provide sufficient capital buffers to cover the exposure during similar economic downturns. These policy-relevant findings suggest a re-calibration of RBA risk weights and may contribute to the current efforts by the Basel Committee on Banking Supervision and others to re-establish sustainable securitization markets and to improve the stability of the financial system.     

Ratings-based credit risk modelling: An empirical analysis

Banks have recently developed new techniques for gauging the credit risk associated with portfolios of illiquid and defaultable instruments. These techniques could revolutionise banks' management of credit risk and could in the longer term serve as a more risk-sensitive basis for calculating regulatory capital on banks' loan books than in Basel 2, the new regulatory capital framework. In this paper we implement a popular credit risk model that exploits the information in credit ratings to determine a portfolio's value-at-risk. Using price data on large eurobond portfolios, we assess, on an out-of-sample basis, how well the model tracks the risks it is supposed to measure.     

Are non-risk based capital requirements for insurance companies binding?

We investigate whether insurers base their solvency margins on risk factors even when operating under a supervisory regime where minimum solvency requirements do not fully take such risk factors into account. To do this, we use a dataset of about 350 Dutch insurers from all major lines of business during the pre-Solvency II period 1995–2005. We find that the levels of insurers’ actual solvency margins are related to their risk characteristics and not to regulatory solvency requirements. Consequently, the vast majority of insurers hold much more capital than required, i.e. non-risk based capital requirements generally are not binding. Requirements are found to affect solvency adjustment behaviour, though. More specifically, below-target capital ratios are raised most rapidly by those insurers whose targets are relatively close to the regulatory minimum. One implication from our results is that, because insurers already follow a risk-based approach, the transition to the new European regulatory framework, Solvency II, is likely to be smooth.     

Is bank diversification a linking channel between regulatory capital and bank value?

This study investigates the interrelationship between bank regulatory capital and bank diversification. We argue that regulatory capital might act as a substitutive mechanism of diversification to alleviate a bank's default risk. As a result, regulatory capital is likely to discourage firms from excessive diversification, which might in turn indirectly improve bank value. Using a sample of listed banks in developed countries from 2011 to 2017, we find that total regulatory capital is inversely associated with bank diversification. Narrower regulatory capital ratios only have a significant association with income-based but not with asset-based diversification. Our results also reveal an indirect effect of regulatory capital on bank value mediated by bank diversification (i.e. indirect-only mediation). Overall, our study provides novel insights into the complementarity of the institutional and strategic domains so as to understand the far-reaching implications of regulation reforms for the strategic behaviour of banking companies.     

Do stress tests affect bank liquidity creation?

We examine the impact of Federal Reserve stress tests from 2009 to 2016 on U.S. bank liquidity creation. Empirical results show that regulatory stress tests have a negative effect on both on-and off-balance sheet bank liquidity creation and asset-side liquidity creation. As banks enter the stress tests, they reduce their liquidity creation to avoid failing the stress tests. These results are consistent with the hypothesis that banks manage their risk exposures to meet higher capital requirements. The negative effect of stress testing on liquidity creation continues to persist in the quarters after the stress tests. Finally, stress test banks appear to increase liability-side liquidity creation. These findings highlight that the enhanced financial stability from greater regulatory scrutiny may be achieved at the expense of financial intermediation.     

M‐PRESS‐CreditRisk: Microprudential and Macroprudential Capital Requirements for Credit Risk under Systemic Stress

M‐PRESS‐CreditRisk is a novel stress testing approach that can help authorities gauge banks' capital adequacy related to credit risk. For the first time, it combines the assessment of microprudential capital requirements under Pillars 1 and 2 and macroprudential buffers in a unified, coherent framework. Its core element is an advanced credit portfolio model—SystemicCreditRisk—built upon a rich, nonlinear dependence structure for correlated bank portfolios. The model is applied to a sample of 12 systemically important German banking groups and delivers measures for systemic credit risk and the banks' contributions to it in both baseline and stress scenarios.     

Diversification and Value-at-Risk

A pervasive and puzzling feature of banks’ Value-at-Risk (VaR) is its abnormally high level, which leads to excessive regulatory capital. A possible explanation for the tendency of commercial banks to overstate their VaR is that they incompletely account for the diversification effect among broad risk categories (e.g., equity, interest rate, commodity, credit spread, and foreign exchange). By underestimating the diversification effect, bank’s proprietary VaR models produce overly prudent market risk assessments. In this paper, we examine empirically the validity of this hypothesis using actual VaR data from major US commercial banks. In contrast to the VaR diversification hypothesis, we find that US banks show no sign of systematic underestimation of the diversification effect. In particular, diversification effects used by banks is very close to (and quite often larger than) our empirical diversification estimates. A direct implication of this finding is that individual VaRs for each broad risk category, just like aggregate VaRs, are biased risk assessments.     

Beyond Basel-2 simplified standardized approach: Credit risk valuation of short-term loan commitments

As alternative to Basel-2 coefficients, this research proposes markup-based risk weights for short-term credit commitments. To do this, Basel-2 credit-conversion and principal-risk factors are replaced by a duration-dependent takedown proportion and a commitment put option that accounts for the nonnormal features of the underlying credit-line marked-to-market value. Put value and takedown proportion are then combined to compute the ‘fair’ capital charge corresponding to the commitment ‘true’ credit risk. As benchmark, the option-based procedure is used next to assess the accuracy of Basel-2 accounting-based capital charges, impose some quasi-market discipline and align regulatory and economic capital requirements. The final step generalises the fair procedure to a new risk-weighting system, which also accounts for the borrowers' risk ratings of public credit agencies.     

Time‐Varying Capital Requirements and Disclosure Rules: Effects on Capitalization and Lending Decisions

We investigate how banks’ capital and lending decisions respond to changes in bank‐specific capital and disclosure requirements. We find that an increase in the bank‐specific regulatory capital requirement results in a higher bank capital ratio, brought about via less asset risk. A decrease in the requirement implies more lending to firms but also less Tier 1 capital and higher bank leverage. We do not observe differences between confidential and public disclosure of capital requirements. Our results empirically illustrate a tradeoff between bank resilience and a fostering of the economy through more bank lending using banks’ capital requirement as policy instrument.     

Banking Competition and Capital Ratios

Empirical studies provide evidence that bank capital ratios exceed regulatory requirements. But why do banks maintain capital levels above regulatory requirements? We use data for more than 2,600 banks from 10 European countries to test recent theories suggesting that competition incentivises banks to maintain higher capital ratios. These theories also predict that banks that engage in arm's length lending have lower capital ratios, and that shareholder rights and deposit insurance characteristics affect capital ratios. Consistent with these theories, our evidence robustly indicates that competition increases capital holdings. Banks that lend at arm's length exhibit lower capital ratios, whereas banks in countries with strong shareholder rights operate with higher capital ratios. We also show some evidence that generous deposit protection schemes that exclude non‐deposit creditors are associated with higher capital ratios. Our results have important policy implications. First, while the traditional view suggests imposing restrictions on bank activities in order to restrain competition, our analysis indicates the opposite, even after adjusting the regressions for risk‐taking. Second, weak shareholder rights undermine market forces that would otherwise encourage banks to hold higher capital ratios.     

Capital shocks, bank asset allocation, and the revised Basel Accord

In contrast to the 1988 Basel Accord (Basel I), the revised risk-based capital standards (Basel II) propose regulatory capital requirements based on credit ratings. This paper develops a theoretical model to analyze how banks will adjust their low and high credit risk commercial loans under the proposed newer standard. Capital-constrained banks respond to an adverse capital shock by reducing high credit risk loans, while under certain circumstances, low credit risk loans may actually increase. When compared to Basel I, it is shown that high-risk loans are reduced more under Basel II, but whether a bank reduces total lending more under Basel I or under the revised standards depends on a complex interaction of factors.     

Why ‘Basel II’ may need a leverage ratio restriction

We analyze regulatory capital requirements where the amount of required capital depends on the level of risk reported by the banks. It is shown that if the supervisors have a limited ability to identify or to sanction dishonest banks, an additional, risk-independent leverage ratio restriction may be necessary to induce truthful risk reporting. The leverage ratio helps to offset the banks’ potential capital savings of understating their risks by (i) reducing banks’ put option value of limited liability ex ante, and by (ii) increasing the banks’ net worth, which in turn enhances the supervisors’ ability to sanction banks ex post.