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.     

Financial contagion risk and the stochastic discount factor

I provide evidence that financial contagion risk is an important source of the equity risk premium. Banks’ contributions to aggregate financial contagion are estimated in a state space framework and linked to systemic risk. Greater bank connectedness today leads to increased systemic risk 3–12 months later. More contagious banks earn significantly greater risk-adjusted returns than less contagious ones and the tradable high contagion-minus-low contagion bank portfolio is priced in the cross-section of stock returns. Stocks that co-move more strongly with contagious banks have greater expected returns. These results are robust to factor model specification, test assets, and time period considered.     

Financial instruments,financial reporting,and financial stability

I review new empirical evidence from the recent financial crisis on the relation between financial reporting and financial stability. I draw the following conclusions: First, there is still no evidence that fair value accounting caused widespread fire sales of asset or contagion. Second, the empirical evidence suggests that accounting and regulation might have contributed to the crisis by allowing several banks to delay actions. Third, even if share prices reacted positively to the relaxation of fair value accounting rules during the crisis, the origin of the problem might be lax rules that allowed banks to run into financial and regulatory problems. Fourth, fair values can be relevant for assets that a bank intends to hold until maturity if that bank strongly relies on short-term financing. Fifth, the recognition of fair values is no substitute for information that allows investors to judge a bank's risk exposure and the validity of reported fair values.     

Financial Networks: Contagion, Commitment, and Private Sector Bailouts

I develop a model of financial networks in which linkages not only spread contagion, but also induce private sector bailouts, where liquid banks bail out illiquid banks because of the threat of contagion. Introducing this bailout possibility, I show that linkages may be optimal ex ante because they allow banks to obtain some mutual insurance even though formal commitments are impossible. However, in some cases (e.g., when liquidity is concentrated among a small group of banks), the whole network may collapse. I also characterize the optimal network size and apply the results to joint liability arrangements and payment systems.     

Crossborder financial contagion to Germany: How important are OTC dealers?

We examine crossborder contagion from a number of financial systems to the German financial system using the information content of CDS prices in a GARCH model. After controlling for common factors which may cause comovement in security prices, we find evidence for contagion from the US and European financial systems. Assessing contagion for dealer and non-dealer banks suggests that contagion from dealer banks is the most prominent source of contagion to the German financial system. While German non-dealer banks are affected both by European and US dealers, only US dealer banks have a contagion effect to German dealer banks.     

Fund Management and Systemic Risk – Lessons from the Global Financial Crisis

Fund managers play an important role in increasing efficiency and stability in financial markets. But research also indicates that fund management in certain circumstances may contribute to the buildup of systemic risk and severity of financial crises. The global financial crisis provided a number of new experiences on the contribution of fund managers to systemic risk. In this article, we focus on these lessons from the crisis. We distinguish between three sources of systemic risk in the financial system that may arise from fund management: insufficient credit risk transfer to fund managers; runs on funds that cause sudden reductions in funding to banks and other financial entities; and contagion through business ties between fund managers and their sponsors. Our discussion relates to the current intense debate on the role the so‐called shadow banking system played in the global financial crisis. Several regulatory initiatives have been launched or suggested to reduce the systemic risk arising from non‐bank financial entities, and we briefly discuss the likely impact of these on the sources of systemic risk outlined in the article.     

On the Contagion Effect in the US Banking Sector

By using the spatial econometrics methodology, this paper investigates the contagion of the risk taking by banks in the US banking sector during 2001 to 2012. In addition, the contagion signals up to the Subprime crisis in 2008 are analyzed and different channels of contagion are studied in order to identify fragile groups of banks. Our analysis reveals that there is no significant contagion transmitted to the whole banking system. However, we observe that the bank contagion is significantly spread locally and for the group of banks that share similar characteristics related to size and bank regulations.     

The effects of news events on market contagion: Evidence from the 2007–2009 financial crisis

In this paper, we use the quantile regression technique along with coexceedance, a contagion measure, to assess the extent to which news events contribute to contagion in the stock markets during the crisis period between 2007 and 2009. Studies have shown that, not only the subprime crisis leads to a global recession, but the effects on the global stock markets have also been significant. We track the news events, both in the UK and the US, using the global recession timeline. We observe that the news events related to ad hoc bailouts of individual banks from the UK have a contagion effect throughout the period for most of the countries under investigation. This, however, is not found to be the case for the news events originating from the US. Our findings regarding the evidence of contagion effects in the UK reinforce the argument that spreads and contagion—an outcome of the risk perception of financial markets—are solely a result of the behaviour of investors or other financial market participants.     

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。     

Modelling the emergence of the interbank networks

Interbank contagion has become a buzzword in the aftermath of the financial crisis that led to a series of shocks to the interbank market and to periods of pronounced market disruptions. However, little is known about how interbank networks are formed and about their sensitivity to changes in key bank parameters (for example, induced by common exogenous shocks or by regulatory initiatives). This paper aims to shed light on these issues by modelling endogenously the formation of interbank networks, which in turn allows for checking the sensitivity of interbank network structures and hence, their underlying contagion risk to changes in market-driven parameters as well as to changes in regulatory measures such as large exposures limits. The sequential network formation mechanism presented in the paper is based on a portfolio optimization model, whereby banks allocate their interbank exposures while balancing the return and risk of counterparty default risk and the placements are accepted taking into account funding diversification benefits. The model offers some interesting insights into how key parameters may affect interbank network structures and can be a valuable tool for analysing the impact of various regulatory policy measures relating to banks’ incentives to operate in the interbank market.     

The near-collapse of LTCM,US financial stock returns,and the fed

We examine both the contagion and the “too-big-to-fail” hypotheses in the context of the long-term capital management (LTCM) crisis in the US financial services industry. Our results show that those commercial and investments banks that were exposed to LTCM lost market values significantly around important events surrounding the near collapse of LTCM, but the losses experienced by investment banks are much higher than the losses faced by commercial banks. Smaller S&L institutions and bigger insurance companies were also affected by the crisis, implying a form of contagion effect in the financial sector. We find some evidence of a `too-big-to-fail' policy with the involvement of the Fed in LTCM, as perceived by the markets.     

The impact of the European sovereign debt crisis on banks stocks. Some evidence of shift contagion in Europe

This paper analyzes the influence of the recent European sovereign debt crisis on banks’ equity returns for 15 countries. Our data span the period December 14th 2007 - March 8th 2013 that encompasses several episodes of economic and financial turmoil since the collapse of the subprime credit market. Our contribution to the literature is twofold. First, we use an explicit multifactor model of equity returns extended with a sovereign risk factor. Second, we adopt a Smooth Transition Regression (STR) framework that allows for an endogenous definition of crisis periods and captures the changes in parameters associated with shift contagion. We find that the negative impact of the European sovereign debt crisis on banks’ equity returns has been mostly confined to European banks, whereas U.S. banks appear to be unharmed by its direct impact and may even have benefited from it. Besides, we find some evidence of shift contagion across Europe.     

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。     

Credit Contagion Channels: Market Microstructure Evidence from Lehman Brothers’ Bankruptcy

Immediately after Lehman Brothers’ bankruptcy, many firms disclosed their financial exposure (or lack thereof) to Lehman. This offers a clean setting to test two credit contagion channels through which a financial firm's bankruptcy can affect other firms—“counterparty risk” and “information transmission” channels. Using market microstructure variables to measure the various dimensions of contagion effects, we provide robust evidence supporting the significance of counterparty risk. Firms with exposure to Lehman suffered more severe negative effects—wider bid‐ask spread, higher price impact, greater information asymmetry, and greater selling pressure—than unexposed firms. We find mixed evidence regarding the information transmission hypothesis.     

Financial contagion: evolutionary optimization of a multinational agent-based model

Over the past two decades, financial market crises with similar features have occurred in different regions of the world. Unstable cross-market linkages during a crisis are referred to as financial contagion. We simulate crisis transmission in the context of a model of market participants adopting various strategies; this allows testing for financial contagion under alternative scenarios. Using a minority game approach, we develop an agent-based multinational model and investigate the reasons for contagion. Although the phenomenon has been extensively investigated in the financial literature, it has not been studied through computational intelligence techniques. Our simulations shed light on parameter values and characteristics which can be exploited to detect contagion at an earlier stage, hence recognizing financial crises with the potential to destabilize cross-market linkages. In the real world, such information would be extremely valuable in developing appropriate risk management strategies. Copyright © 2009 John Wiley & Sons, Ltd.     

机构集聚、风险传染与香港银行的系统性风险

本文研究作为银行金融机构集聚的香港国际金融中心,经受外部冲击后银行系统脆弱性的内生性及传染机理。本文把系统性风险的形成划分为共同冲击和相互传染两个过程,选取香港上市银行2006年到2011年的股价收益率为研究对象,分别研究中资、港资及外资三个组别的金融机构个体风险特征,运用分位数回归模型,通过测量香港银行体系的条件风险价值,判断香港银行的系统性风险,并分析影响香港银行体系脆弱性的外生性因素和内生性因素。结果表明,外资银行对共同冲击的抵抗能力较强,而港资银行的抵抗能力优于内地银行;金融机构间的传染和风险溢出效应会导致系统性风险的增加,而且不同规模银行对于系统性风险的溢出程度不一样,规模较大银行的溢出效应较为明显。     

Credit risk transfer and contagion

Some have argued that recent increases in credit risk transfer are desirable because they improve the diversification of risk. Others have suggested that they may be undesirable if they increase the risk of financial crises. Using a model with banking and insurance sectors, we show that credit risk transfer can be beneficial when banks face uniform demand for liquidity. However, when they face idiosyncratic liquidity risk and hedge this risk in an interbank market, credit risk transfer can be detrimental to welfare. It can lead to contagion between the two sectors and increase the risk of crises.     

Financial liberalization and contagion with unobservable savings

How does the presence of decentralized market-based channels for borrowing and lending affect financial integration and financial contagion? To answer this question, I develop a two-country model of financial intermediation, where banks have access to country-specific investment technologies, and agents can borrow and lend in an international hidden market. In this environment, the possibility of hidden borrowing and lending has three main effects. First, it improves welfare with respect to the autarkic equilibrium, by allowing gains from “hidden” financial integration. Second, it halts the process of “official” financial integration. Third, it lowers the resilience of the economy to unexpected shocks to fundamentals.     

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。     

Bank/sovereign risk spillovers in the European debt crisis

This paper investigates contagion between bank and sovereign default risk in Europe over the period 2007–2012. We define contagion as excess correlation, i.e. correlation between banks and sovereigns over and above what is explained by common factors, using CDS spreads at the bank and at the sovereign level. Moreover, we investigate the determinants of contagion by analyzing bank-specific as well as country-specific variables and their interaction. Using the EBA’s disclosure of sovereign exposures of banks, we provide empirical evidence that three contagion channels are at work: a guarantee channel, an asset holdings channel and a collateral channel. We find that banks with a weak capital buffer, a weak funding structure and less traditional banking activities are particularly vulnerable to risk spillovers. At the country level, the debt ratio is the most important driver of contagion. Furthermore, the impact of government interventions on contagion depends on the type of intervention, with outright capital injections being the most effective measure in reducing spillover intensity.