A network model of systemic risk: stress testing the banking system1

Although there are many definitions of systemic risk, most agree that it manifests itself by an initial shock that results in the failure of one or more banks and then spreads out to the entire system by a contagion mechanism which can result in the failure of more banks in the system. Assuming that bank failures in the initial shock are randomly dependent on the failure probabilities of the individual banks and that the ensuing contagion process is deterministic, depending on interbank exposures, in this paper we propose a network model to analyse systemic risk in the banking system that, in contrast to other proposed models, seeks to obtain the probability distribution of losses for the financial system resulting from the shock/contagion process. Thus, calculating the probabilities of joint failures by simulation and assuming that the matrix of bilateral interbank exposures is known, we represent systemic risk in the financial system by means of a graph and use discrete modelling techniques to characterize the dynamics of contagion and corresponding losses within the network. The probability distribution of losses, risk profile for the Mexican banking system, is obtained through an efficient, complete enumeration procedure of all possible bank default events in the system. This, in turn, allows the use of the wide variety of well-established risk measures to describe the fragility of the financial system. Additionally, the model allows us to perform stress tests along both the bank default probabilities and the interbank exposures and is used to assess the risk of the Mexican banking system. Copyright © 2009 John Wiley & Sons, Ltd.     

Measuring Integrated Market and Credit Risk in Bank Portfolios: An Application to a Set of Hypothetical Banks Operating in South Africa

The banking crises of the ‘90s emphasize the need to model the connections between financial environment volatility and the potential losses faced by financial institutions resulting from correlated market and credit risks. Due to the number of variables that must be modeled and the complexity of the relationships an analytical solution is not feasible. We present here a numerical solution based on a simulation model that explicitly links changes in the relevant variables that characterize the financial environment and the distribution of possible future bank capital ratios. This forward looking quantitative risk assessment methodology allows banks and regulators to identify potential risks before they materialize and make appropriate adjustments to bank portfolio credit qualities, sector and region concentrations, and capital ratios on a bank by bank basis. It also has the potential to be extended so as to assess the risks of correlated failures among a group of financial institutions (i.e., systemic risk analyses). This model was applied by the authors to the study of the risk profile of the largest South African Banks in the context of the Financial System Stability Assessment program undertaken by the IMF in 1999. In the current study, we apply the model to various hypothetical banks operating in the South African financial environment and assess the correlated market and credit risks associated with business lending, mortgage lending, asset and liability maturity matches, foreign lending and borrowing, and direct equity, real estate, and gold investments. It is shown to produce simulated financial environments (interest rates, exchange rates, equity indices, real estate price indices, commodity prices, and economic indicators) that match closely the assumed parameters, and generate reasonable credit transition probabilities and security prices. As expected, the credit quality and diversification characteristics of the loan portfolio, asset and liability maturity mismatches, and financial environment volatility, are shown to interact to determine bank risk levels. We find that the credit quality of a bank's loan portfolio is the most important risk factor. We also show the risk reduction benefits of diversifying the loan portfolio across various sectors and regions of the economy and the importance of accounting for volatility shocks that occur periodically in emerging economies. Banks with high credit risk and concentrated portfolios are shown to have a high risk of failure during periods of financial stress. Alternatively, banks with lower credit risk and broadly diversified loan portfolios across business and mortgage lending are unlikely to fail even during very volatile periods. Asset and liability maturity mismatches generally increase bank risk levels. However, because credit losses are positively correlated with interest rate increases, banks with high credit risk may reduce overall risk levels by holding liabilities with longer maturities than their assets. Risk assessment methodologies which measure market and credit risk separately do not capture these various interactions and thus misestimate overall risk levels.     

Financial networks and systemic risk vulnerabilities: A tale of Indian banks

This study identifies the nature and direction of unprecedented upheavals in the Indian banking sector which is linked to credit market asymmetry. A tail-driven network approach with a mixed sample of banks and firms exhibits the characteristics of the twin-balance-sheet syndrome. We construct the networks with a degree of interconnectedness at different quantiles and identify major systemic risk emitters and receivers. Furthermore, we find a spillover of the riskiness of deep-in-debt firms to banks. Smaller banking institutions evince a greater connection to banks and firms than larger ones. Our results are valuable for policymakers formulating financial stabilization policies and investors considering Indian markets for various opportunities.     

Investor ambiguity,systemic banking risk and economic activity: The case of too-big-to-fail

This paper examines the relationship between investors' ambiguity in the financial options market and systemic banks' risk. Eliciting ambiguity information from option pricing data on the twelve major U.S. banks between 2003 and 2010, we show that higher behavioral deviations from risk-neutral and Bayesian valuation (i.e., investor ambiguity) are associated with higher systemic banks' downside, market and credit risks. Consistent with behavioral explanations, we confirm the detrimental effect of ambiguity on financial market outcomes and find strong evidence of ambiguity among call and put option holders. Variance decomposition indicates that such a pattern of behavior explains a significant proportion of U.S. banking risk variance. This effect is more pronounced during periods of economic turbulence and bank stress (i.e., the 2007–2009 crisis), and holds after controlling for size, tail risk, implied volatility, and volatility of volatility dynamics. We also document that ambiguity from the financial market has a depressing impact on real economic activity, including capacity utilization, non-farm payrolls and overall economic performance. Our findings are robust to alternative specifications of ambiguity such as multiple priors and expected utilities with uncertain probabilities.     

Tail Risk Networks of Insurers Around the Globe: An Empirical Examination of Systemic Risk for G-SIIs vs Non-G-SIIs

In this article, we investigate systemic risk of 157 insurers around the globe. We construct tail risk networks among these insurers using a single-index model for quantile regressions with a variable selection technique. We develop a new network-based systemic risk indices, taking into account expected tail losses of insurers, direct and indirect contagion effects, and the time-varying strength of tail risk spillover. Our systemic risk indices successfully recognize global systemically important insurers (G-SIIs). We find that on average G-SIIs are more systemically relevant than non-G-SIIs, particularly during the recent U.S. financial crisis. We also find a small group of non-G-SIIs that are more important than G-SIIs. Our results have significant implications for systemic risk regulation.     

宏观审慎政策协调能否抑制国际性银行危机传染？——基于跨境金融关联视角的实证研究

本文基于跨境金融关联视角对宏观审慎政策能否抑制国际性银行危机传染这一重要的理论与实践问题进行了实证研究。选取亚洲金融危机和全球金融危机时期遭受冲击的10个代表性国家作为样本,构建Logit模型和多元回归模型探讨本国及具有金融关联的国家协调实施宏观审慎政策对本国系统性银行危机传染的影响。研究表明,具有金融关联的国家出现金融危机会显著增加本国系统性银行危机的发生概率,具有金融关联的国家实施宏观审慎政策对本国信贷的影响比对房价的影响更明显,本国及具有金融关联的国家协调实施宏观审慎政策会显著降低本国系统性银行危机的发生概率。在调整银行危机指标及考虑贸易关联和流动性风险的影响后,研究结果依然保持稳健。本文的研究结论揭示了加强宏观审慎政策协调有助于维护全球金融稳定,对于中国政策当局强化宏观审慎管理具有极其重要的政策含义。     

Systemic Risk,Financial Crisis,and Credit Risk Insurance

Differing from conventional insurance firms whose underwriting business does not contribute to systemic risk, credit risk insurance companies providing credit protections for debt obligations are exposed to systemic risk. We show that credit risk insurers (CRIs) underperformed conventional insurance companies during the 2007–2009 financial crisis, and such underperformance is attributed to the greater systemic risk of CRIs. We also find that the credit spreads of insured bonds increase significantly after their insurers are downgraded or put in the negative watch list. We control for alternative factors affecting bond credit spreads and the result is robust.     

Credit information sharing in the nexus between charter value and systemic risk in Asian banking

In this paper, we assess whether the link between charter value and systemic risk in banking is affected by credit information sharing at the country level. Using a sample of Asian listed banks, we document that banks with higher charter value exhibit lower systemic risk because these banks hold more capital. Nevertheless, we find that the self-disciplining role of charter value in banking is more pronounced for countries with lower depth of credit information sharing. Specifically, our findings also reveal that higher charter value alleviates systemic risk and increases capitalization, particularly in countries with lower quality of private credit bureaus. These findings suggest that higher charter value can be detrimental for financial stability due to an increase in bank systemic risk, particularly when private credit bureaus are of better quality. In order to overcome bank systemic risk, this paper advocates the importance of strengthening bank competition to limit charter value, in addition to promoting the development of private credit bureaus.     

Systemic Bank Risk in Brazil: A Comprehensive Simulation of Correlated Market, Credit, Sovereign and Inter-Bank Risks

In this study we present a comprehensive forward‐looking portfolio simulation methodology for assessing the correlated impacts of market risk, private sector and Sovereign credit risk, and inter‐bank default risk. In order to produce better integrated risk assessment for banks and systemic risk assessments for financial systems, we argue that reasonably detailed modeling of bank asset and liability structures, loan portfolio credit quality, and loan concentrations by sector, region and type, as well as a number of financial and economic environment risk drivers, is required. Sovereign and inter‐bank default risks are increasingly important in the current economic environment and their inclusion is an important model extension. This extended model is demonstrated through an application to both individual Brazilian banks (i.e., 28 of the largest banks) and groups of banks (i.e., the Brazilian banking system) as of December 2004. When omitting Sovereign risk, our analysis indicates that none of the banks face significant default risk over a 1‐year horizon. This low default risk stems primarily from the large amount of government securities held by Brazilian banks, but also reflects the banks' adequate capitalizations and extraordinarily high interest rate spreads. We note that none of the banks which we modeled failed during the very stressful 2007‐2008 period, consistent with our results. Our results also show that a commonly used approach of aggregating all banks into one single bank, for purposes of undertaking a systemic banking system risk assessment, results in a misestimate of both the probability and the cost of systemic banking system failures. Once Sovereign risk is considered and losses in the market value of government securities reach 10% (or higher), we find that several banks could fail during the same time period. These results demonstrate the well known risk of concentrated lending to a borrower, or type of borrower, which has a non‐zero probability of default (e.g., the Government of Brazil). Our analysis also indicates that, in the event of a Sovereign default, the Government of Brazil would face constrained debt management alternatives. To the best of our knowledge no one else has put forward a systematic methodology for assessing bank asset, liability, loan portfolio structure and correlated market and credit (private sector, Sovereign, and inter‐bank) default risk for banks and banking systems. We conclude that such forward‐looking risk assessment methodologies for assessing multiple correlated risks, combined with the targeted collection of specific types of data on bank portfolios, have the potential to better quantify overall bank and banking system risk levels, which can assist bank management, bank regulators, Sovereigns, rating agencies, and investors to make better informed and proactive risk management and investment decisions.     

Geographic diversification in banking

In the aftermath of the 2007–2009 crisis, banks claiming positive diversification benefits are being met with skepticism. Nevertheless, diversification might be important and sizable for some large internationally active banking groups. We use a universally applicable correlation matrix approach to calculate international diversification effects, in which bank subsidiaries are treated as individual assets of the banking group portfolio. We apply the framework to 49 of the world's largest banking groups with significant foreign business units over the 1992–2009 period. Focusing on the most important risk in banking, credit risk, we find that allowing for geographical diversification could reduce banks’ credit risk by 1.1% on average, with risk reduction ranging from negligible up to 8%.     

Securitization and systemic risk: An empirical investigation on Italian banks over the financial crisis

This research examines the effects of securitization on the bank's risk exposure both in terms of individual expected shortfall and marginal expected shortfall as a measure of systemic risk. The relationship between securitization activity and tail risks is especially relevant in light of the consequences for financial stability, both for the individual securitizing banks and for the market as a whole, as the financial crisis 2007–2008 reveals. By using a sample of Italian listed banks over the period 2000–2009, we find that securitizing banks have, on average, higher expected losses in case of extreme events. This adds new evidence on the main findings in the literature that focused on the evidence that risk transfer through securitization is relatively insignificant compared to the risk retained by the originating bank. We show that this risk retention is in terms of an increase of tail risk. We also find that securitization increases the probability of banks to become “systemically” riskier, but we find no difference when comparing the pre-crisis with the post-crisis period. This suggests that the systemic exposures of Italian banks are still as high as before the crisis with severe implications for financial stability.     

How likely is contagion in financial networks?

Interconnections among financial institutions create potential channels for contagion and amplification of shocks to the financial system. We estimate the extent to which interconnections increase expected losses and defaults under a wide range of shock distributions. In contrast to most work on financial networks, we assume only minimal information about network structure and rely instead on information about the individual institutions that are the nodes of the network. The key node-level quantities are asset size, leverage, and a financial connectivity measure given by the fraction of a financial institution’s liabilities held by other financial institutions. We combine these measures to derive explicit bounds on the potential magnitude of network effects on contagion and loss amplification. Spillover effects are most significant when node sizes are heterogeneous and the originating node is highly leveraged and has high financial connectivity. Our results also highlight the importance of mechanisms that go beyond simple spillover effects to magnify shocks; these include bankruptcy costs, and mark-to-market losses resulting from credit quality deterioration or a loss of confidence. We illustrate the results with data on the European banking system.     

What Is Systemic Risk?

The traditional view of risk in a financial system is that it is the summation of individual risks within the system. However, the financial crisis that started in 2007 has driven home that this view of risk is inadequate. It is the interactions of financial institutions and markets that determine the systemic risks that drive financial crises. We identify four types of systemic risk. These are (i) panics—banking crises due to multiple equilibria; (ii) banking crises due to asset price falls; (iii) contagion; and (iv) foreign exchange mismatches in the banking system.     

Realized bank risk during the great recession

We find that certain bank characteristics—aggressive credit growth, less reliance on deposit funding, and size—prior to the 2007−2009 crisis are consistently related to the systemic dimensions of bank risk during the crisis. Exposures to real estate play a major role explaining this relationship: Banks with larger real estate betas exhibited higher levels of systemic risk during the crisis. The impact of real estate betas on systemic risk increases for larger banks, following aggressive credit growth policies in the presence of housing bubbles. We show that the relationship between bank characteristics and risk could also be detected using measures of systemic risk calculated prior to the financial crisis.     

Assessing the credit risk of money market funds during the eurozone crisis

This paper measures credit risk in prime money market funds (MMFs) and studies how such credit risk evolved during the eurozone crisis of 2011–2012. To accomplish this, we estimate the annualized expected loss on each fund's portfolio. We also calculate by Monte Carlo the cost of insuring a fund against losses amounting to over 50 basis points. We find that credit risk of prime MMFs, though small, doubled from 12 basis points in June 2011 to 23 basis points in December 2011 before receding in 2012. Contrary to common perceptions, this did not primarily reflect funds’ credit exposure to eurozone banks because funds took measures to reduce this exposure. Instead, credit risk in prime MMFs rose because of the deteriorating credit outlook of banks in the Asia/Pacific region. We conclude that the increase in the credit risk of prime MMFs in the second half of 2011 reflected contagion in the worldwide banking system coupled with slowing global economic growth, not actions taken by MMFs.     

How credible is a too-big-to-fail policy? International evidence from market discipline

This paper analyzes in an international sample of banks from 104 countries if the sensitivity of the cost of deposits to bank risk varies across banks depending on their systemic and absolute size. We analyze a period before the 2007 financial crisis and control for endogeneity of bank size, intervention policies in past banking crises, and soundness of countries’ public finances. Our results are consistent with the predominance of the too-big-to-fail hypothesis, although this effect is stronger in countries that did not impose losses on depositors in past banking crises and in countries with sounder public finances.     

Bank risk,competition and bank connectedness with firms: A literature review

The outbreak of the 2007–2009 financial crisis and of the European sovereign debt crisis again raised questions about the vulnerability and the behaviour of banking institutions. The unconventional monetary policies that followed have flattened the yield curve and created a low interest rates environment. This can give rise to risk-taking behaviour from banks and can therefore undermine the stability of the banking system with negative impact of the credit supply, corporate investment and real economy. This article proposes a literature review on the main determinants of bank lending and risk-taking decisions, going through the competition in the banking market, the bank connectedness with firms and the role of monetary and banking authorities. The systemic risk concept is also discussed as well as its drivers and potential measures that should be monitored by prudential authorities in order to preserve financial stability.     

Financial networks,bank efficiency and risk-taking

Networks with a core–periphery topology are found in many financial systems across different jurisdictions. Though the theoretical and structural aspects of core–periphery networks are clear, the consequences that core–periphery structures bring for banking efficiency stand as an open question. We address this gap in the literature by providing insights as to how the structure of financial networks can affect bank efficiency. We find that core–periphery structures are cost efficient for banks, which is a characteristic that encourages the participation of banks in financial networks. On the downside, we also show that core–periphery structures are risk-taking inefficient, because they imply higher systemic risk levels in the financial system. In this way, regulators should be aware of the excessive risk inefficiency that arises in the financial system due to individual decisions made by banks in the network.     

Government interventions and default risk: Does one size fit all?

We examine the effectiveness of the financial sector rescue packages provided by the national governments during the 2008 financial crisis. This study questions the implicit assumption that government interventions have an uniform effect on the default risk of individual banks. After testing the results for sensitivity, our main findings suggest that there exists a significant negative relationship between the announcement of the financial sector rescue packages and the daily change of the credit default premium. However, quantile regressions show that the effectiveness of these packages differs across banks: most interventions do not decrease the risk of intermediate to low-risk banks, while they do reduce the risk of high-risk banks. Besides, we find that interventions aimed at specific financial institutions are more effective in restraining banking risk than broad interventions taken to stabilize the financial market as a whole.     

Multilayer information spillover networks between oil shocks and banking sectors: Evidence from oil-rich countries

There is no doubt that oil price shocks significantly affect oil-producing countries' macroeconomic fundamentals and financial stability, mainly in crisis times. The recent oil price shocks, coupled with the COVID-19 pandemic, motivated us to investigate the connectedness and risk transmission among oil shocks and banking sectors in the Gulf Cooperation Council (GCC) economies from June 30, 2006, to September 9, 2021. Thus, we construct multilayer information spillover networks between oil price shocks and GCC banking sectors. The empirical results show that the Bahrain banking sector depicts the highest connectedness and risk transmission with oil price shocks on the extreme risk spillover layer. In addition, Kuwait and the United Arab Emirates are highly connected to oil demand shocks. Furthermore, we find a substantial increase in extreme risk spillover and volatility spillover layers during the COVID-19 period. The results of this paper have some important implications for regional portfolio risk management, alleviating systemic risk, and developing hedging and investment strategies.