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.     

基于房地产市场的我国系统性金融风险测度与预警研究

本文阐释了基于房地产市场的系统性金融风险形成机制,据此建立了分阶段、跨部门的房地产市场的系统性金融风险网络模型,并运用2006-2017年16家上市银行数据,分析和测度了我国房价大幅下跌所引发的系统性金融风险水平和结构,构建了基于房地产市场的系统性金融风险预警指标并进行测算。研究发现:在房价下跌30%的压力情景下,我国金融体系的潜在总损失总体呈级数式上升,年均增长22.70%;基于房地产市场的系统性金融风险值(SR)呈现先上升后波动下降的总体趋势;系统性金融风险(SR)的脆弱性指标(FLI)整体呈现波浪式振荡变化,且与房地产贷款/权益整体呈反向变动,系统性金融风险(SR)的传染性指标(CTI)在2012-2017年呈持续下降趋势,且与金融市场压力指数、金融机构间资产占总资产比重呈现出高度的一致性变化趋势。最后,基于房地产市场的系统性金融风险预警指标(SRWI)值呈收敛式振荡走势,表明基于房地产市场的系统性金融风险总体可控且呈收敛式下降。     

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.     

基于房地产市场的我国系统性金融风险测度与预警研究

本文阐释了基于房地产市场的系统性金融风险形成机制,据此建立了分阶段、跨部门的房地产市场的系统性金融风险网络模型,并运用2006-2017年16家上市银行数据,分析和测度了我国房价大幅下跌所引发的系统性金融风险水平和结构,构建了基于房地产市场的系统性金融风险预警指标并进行测算。研究发现:在房价下跌30%的压力情景下,我国金融体系的潜在总损失总体呈级数式上升,年均增长22.70%;基于房地产市场的系统性金融风险值(SR)呈现先上升后波动下降的总体趋势;系统性金融风险(SR)的脆弱性指标(FLI)整体呈现波浪式振荡变化,且与房地产贷款/权益整体呈反向变动,系统性金融风险(SR)的传染性指标(CTI)在2012-2017年呈持续下降趋势,且与金融市场压力指数、金融机构间资产占总资产比重呈现出高度的一致性变化趋势。最后,基于房地产市场的系统性金融风险预警指标(SRWI)值呈收敛式振荡走势,表明基于房地产市场的系统性金融风险总体可控且呈收敛式下降。     

Systemic risk and dynamics of contagion: a duplex inter-bank network

This paper constructs a duplex banking network formed by credit relationships and information interaction via the banks’ balance sheet to model the structure of systemic risk and investigate the dynamic mechanism of contagion in terms of default and liquidity infection along with the factors that affect the extent of the contagion. We systematically explain the role that duplex banking networks play in different aspects of risk contagion. Through theoretical analysis and simulations, we conclude that asymmetric information interaction would increase the inflexibility of the system, which leads to liquidity shortage and possibly the collapse of the whole market. The weakness of systemic risk in the interior of the complex banking system can be characterized by the partial discount factor using illiquid assets in the information network. By improving the connectedness of the information network of the duplex networks, the spread of contagion can be partially slowed.     

基于共同冲击和异质风险叠加传导的风险传染研究——来自中国上市银行网络的传染模拟

本文将银行系统遭遇外部共同冲击作为研究起点,建立了一个共同冲击和异质风险交互传导与放大的简化模型,冲击的传导包括“原始冲击”、“增量冲击”和“违约冲击”三个风险传染阶段。基于2018年我国15家上市银行的股票收益率和年报数据、2006年至2018年的银行评级数据,本文构建了贝叶斯分层图模型和银行间拆借矩阵,并利用蒙特卡洛模拟测度不同触发银行所引发的系统性风险损失、单个银行的系统性风险杠杆能力(文中定义为“传染乘数”指标)以及政府监管介入的效果。模拟结果显示:共同冲击损失远大于异质风险损失;规模和网络关联性是决定传染乘数的重要因素,且当规模因素不突出时,网络关联性对传染乘数的决定作用相对更强,极容易出现小规模、高关联性银行具有较高的传染乘数;当银行风险资产损失率在10%至25%之间时,造成系统性风险损失的杠杆能力普遍增强;政府监管介入能较好地降低系统性风险。本研究的相关结论为系统性风险的监管设计提供经验证据和参考。     

非寿险承保风险引发系统性风险的复杂网络分析

本文基于我国财险业2009~2018年数据,用复杂网络理论模型构建了财险业承保业务网络,并模拟了承保风险传染过程,分析了承保风险对财险业系统性风险的影响轨迹及程度。研究发现,我国财险业承保业务网络的联系越来越密切,承保风险的增加会引发传染风险,进而导致爆发系统性风险。但当前我国财险业整体稳定,只有发生1600亿元及以上的初始损失时,才会有保险机构陷入危机;当初始损失大于8500亿元时,才会有保险机构因传染风险而陷入危机。在承保风险的传染过程中,损失至少以数倍的速度下降;保险机构主要在承保风险和前两轮传染中损失较大,在后续传染轮次陷入危机的可能性极低。因此,防范巨灾风险、监管重点公司、探索巨灾转移机制并建立承保风险预警机制显得比较重要。     

中国房地产企业间系统性风险溢出效应分析——基于尾部风险网络模型

本文以2007—2021年沪深A股上市房企为样本,首先基于SIM单指数分位数回归技术提出测量系统性风险的新指标SIM-CoVaR,并结合前沿的TENET网络模型,构造跨房地产企业风险动态传染的尾部风险网络,然后采用块模型探究房地产市场系统性风险溢出的聚类性、触发机制及传播路径,最后考察网络整体结构和宏观经济变量对房地产市场系统性风险溢出的影响。研究表明:(1)我国房地产企业间存在明显的系统性风险联动性和溢出效应,在市场动荡时期房地产部门是金融风险溢出的放大器;(2)评估系统重要性节点企业时,除考虑企业规模等内部属性,还应考虑房企间关联结构,利用系统性风险指数可有效捕捉网络中系统重要性节点;(3)跨房企的系统性风险溢出具有显著的聚类特征,尾部风险网络可被划分为4个不同的功能模块,各模块的成员及其角色呈现明显的时变特性,监管部门可据此从供给端“因企施策”;(4)网络聚集性、网络效率和网络匹配性的降低能显著降低房地产市场的系统性风险溢出效应。本文从企业微观层面探讨房地产市场风险的形成机制,为促进房地产业健康发展和防范化解宏观层面的系统性金融风险提供参考。     

Can Loan Valuation Adjustment (LVA) approach immunize collateralized debt from defaults?

This study focuses on structuring tangible asset backed loans to inhibit their endemic option to default. We adapt the pragmatic approach of a margin loan in the configuring of collateralized debt to yield a quasi‐default‐free facility. We link our practical method to the current Basel III (2017) regulatory framework. Our new concept of the Loan Valuation Adjustment (LVA) and novel method to minimize the LVA converts the risky loan into a quasi risk‐free loan and achieves value maximization for the lending financial institution. As a result, entrepreneurial activities are promoted and economic growth invigorated. Information asymmetry, costly bailouts and resulting financial fragility are reduced while depositors are endowed with a safety net equivalent to deposit insurance but without the associated moral hazard between risk‐averse lenders and borrowers.     

中小企业集合债券总体信用风险度量研究

中小企业集合债券总体信用风险既包括系统风险产生的周期性违约风险,又包括相互关联关系导致的传染性违约风险。首先通过对因素模型的改进构建模型Ⅰ,研究集合债券的周期性违约风险;在此基础上引入违约传染建立模型Ⅱ,分析违约传染对违约概率及违约相关性的影响,研究集合债券的总体信用风险。最后基于模型Ⅱ进行算例研究,得出结论：企业间的相互关联关系降低了其1次违约概率,增加了其多次违约概率即违约相关性。     

Credit risk spillovers and cash holdings

This paper examines how credit risk spillovers affect corporate financial flexibility. We construct separate empirical proxies to disentangle the two channels of credit risk spillovers—credit risk contagion (CRC), where one firm's default increases the distress likelihood of another; and product market rivalry (PMR), where the same default strengthens the position of a competitor. We show that firms facing greater CRC have weaker subsequent operating performance and must contend with less favorable bank loan terms. Meanwhile, they accumulate more cash by issuing equity, selling assets, and reducing investment and payout. In contrast, PMR generally has opposite, albeit weaker, effects. Our findings suggest that credit risk spillovers, especially CRC, play an important role in corporate liquidity management.     

Resaleable debt and systemic risk

Many debt claims, such as bonds, are resaleable; others, such as repos, are not. There was a fivefold increase in repo borrowing before the 2008–2009 financial crisis. Why? Did banks’ dependence on non-resaleable debt precipitate the crisis? In this paper, we develop a model of bank lending with credit frictions. The key feature of the model is that debt claims are heterogenous in their resaleability. We find that decreasing credit market frictions leads to an increase in borrowing via non-resaleable debt. Such borrowing has a dark side: It causes credit chains to form, because, if a bank makes a loan via non-resaleable debt and needs liquidity, it cannot sell the loan but must borrow via a new contract. These credit chains are a source of systemic risk, as one bank’s default harms not only its creditors but also its creditors’ creditors. Overall, our model suggests that reducing credit market frictions may have an adverse effect on the financial system and even lead to the failures of financial institutions.     

Distance to default,subordinated debt,and distress indicators in the banking industry*

The recent financial crisis has highlighted the inadequacy of present supervisory arrangements to identify reliable ex‐ante indicators of banking distress. For a sample of US bank holding companies, we analyse the extent to which distance to default based on market data can be explained using accounting‐based indicators of risk. We show that a larger number of bank fundamentals help predict default for institutions that issue subordinated debt. For banks that issue sub‐debt, we find that higher charter values and low bank capitalizations further increase the power of bank fundamentals to predict default risk.     

THE INFORMATIONAL ROLE OF BANK LOAN RATINGS

We analyze the relatively new phenomenon of credit ratings on syndicated loans, asking first whether they convey information to the capital markets. Our event studies show that initial loan ratings and upgrades are not informative, but downgrades are. The market anticipates downgrades to some extent, however. We also examine whether public information reflecting borrower default characteristics explains cross‐sectional variation in loan ratings and find that ratings are only partially predictable. Our evidence suggests that loan and bond ratings are not determined by the same model. Finally, we estimate a credit spread model incorporating bank loan ratings and other factors reflecting default risk, information asymmetry, and agency problems. We find that ratings are related to loan rates, given the effect of other influences on yields, suggesting that ratings provide information not reflected in financial information. Ratings may capture idiosyncratic information about recovery rates, as each of the agencies claims, or information about default prospects not available to the market.     

Systemic Risk in the Chinese Shadow Banking System: A Sector-Level Perspective

We propose to measure the systemic risk in the shadow banking sector. Instead of testing how many institutions will fail due to the initial breakdown of one institution as extant network models do, we associate the systemic risk of one shadow banking sector with the total amount of unexpected losses it might generate both directly and indirectly. Our model focuses on balance sheet contagion and applies a loop algorithm to risk transfer. The result shows that trust companies were the main culprit of financial instability and commercial banks assumed the main risks over 2007–12 in the Chinese shadow banking system.     

银行信贷资产证券化信用风险度量及传染研究——基于修正KMV模型和MST算法的实证

精准科学地度量和描述信用风险及传染机制有利于银行信贷资产证券化的高效健康发展和货币市场系统性风险的防范.运用修正KMV模型测度银行信贷资产证券化产品在不同时期的信用风险,并采用最小生成树(MST)算法考察银行间信用风险的传染机制.结果显示:政策性银行和大型商业银行发行的产品在各个时期信用风险均处于较低水平;股份制银行、城商行和农商行发行的产品违约率前期略高于前两类银行,但后期明显下降;后三类银行位于银行股票收益率网络的中心位置,具有传递信息和维系网络稳定的重要作用.     

Bankruptcy,overlapping directors,and bank loan pricing

Using a sample of loan facilities borrowed by firms that share directors with bankrupt firms, this study investigates whether the overlapping directors are a transmission channel of the bankruptcy contagion effect in the bank loan market and, if so, what the underlying mechanism is. We find that firms are charged higher loan spreads in the period following the bankruptcy filing of a firm with a common director and that overlapping directors are a relevant channel for the bankruptcy contagion effect, in addition to other channels identified in literature. We also find that the negative contagion effect on loan pricing is most likely driven by the overlapping directors' reputation loss due to their involvement in bankruptcy events, and not by competing hypotheses, such as director distraction and director career concern/experience. Further analyses reveal that the adverse contagion impact on loan spreads is more pronounced when overlapping directors have greater influence over corporate policies or when their reputation is more seriously damaged. Meanwhile, the contagion effect is mitigated when interlocked firms have a higher-quality board. These results further support our evidence of the director reputation loss hypothesis. We strengthen the identification strategy to establish causality. In sum, our study identifies common directors as a channel of bankruptcy contagion effects on loan pricing and director reputation loss as an underlying mechanism.     

A set-valued Markov chain approach to credit default

We propose a novel credit default model that takes into account the impact of macroeconomic factors and intergroup contagion on the defaults of obligors. We use a set-valued Markov chain to model the default process, which includes all defaulted obligors in the group. We obtain analytic characterizations for the default process and derive pricing formulas in explicit forms for synthetic collateralized debt obligations (CDOs). Furthermore, we use market data to calibrate the model and conduct numerical studies on the tranche spreads of CDOs. We find evidence to support that systematic default risk coupled with default contagion could have the leading component of the total default risk.     

失信风险传染会影响债券定价吗？——基于担保网络大数据的实证研究

在债券定价研究中不仅应该考虑企业自身的信用风险,还应该考虑相关网络组织的传染风险。本文基于43万笔非金融企业间的担保数据,构建了企业信用担保网络,发现失信风险作为一种广义的信用风险,在担保网络中具有传染效应,该传染效应能够影响债券的信用利差。企业的失信行为产生了三类传染效应,一是直接传染效应,无论是发债主体的担保人出现失信行为,还是被担保人出现失信行为,都会引起发债主体的信用利差上升;二是局部感染效应,如果局部担保网络中失信主体的占比提升,可能引起投资者对发债主体的“团体处罚”,导致信用利差上升;三是全局扩散效应,失信信息沿担保网络向整个市场扩散,导致债券信用利差上升。从企业所有制来看,民营企业主要受微观的直接传染效应和中观的局部感染效应影响;而国有企业主要受全局扩散效应影响;被担保人的失信风险对两类企业都有显著影响。失信风险传染效应会降低企业的再融资能力,其中局部感染效应导致企业次年的借款融资额下降,全局扩散效应导致企业次年的债券融资额下降。     

Multilayer financial networks and systemic importance: Evidence from China

In this paper, we develop a multilayer network structure and reveal the relationship between network structure and systemic risk. Unlike many previous studies, our model considers both liability and cross-holding of shares between financial institutions simultaneously. We propose a new systemic risk measurement by exploring the dynamic mechanism of financial contagion in the multilayer network. We display the network structure of Chinese financial institutions, including connectivity and diversity, and identify the systemic importance of them. We demonstrate that the multilayer network plays a non-linear role in financial risk spreading. Using the panel regression model and several experiment evidences, we show that the systemic risk can be explained more effectively by the linkage diversity more than the connectivity at both the institutional level and the system level. Our results highlight the importance of considering contagion mechanisms that go beyond a simple single-layer network structure.