The great entanglement: The contagious capacity of the international banking network just before the 2008 crisis

Systemic risk among the network of international banking groups arises when financial stress threatens to crisscross many national boundaries and expose imperfect international coordination. To assess this risk, we consider three decades of data on the cross-border interbank market. We use Rosvall and Bergstrom’s (2008) information theoretic map equation to partition banking groups from 21 countries into modules that reveal the contagious capacity of the network. We show that in the late 1980s four important financial centers formed one large super cluster that was highly contagious in terms of transmission of stress within its ranks, but less contagious on a global scale. But the expansion leading to the 2008 crisis left more transmitting hubs sharing the same total influence as a few large modules had previously. We show that this greater entanglement meant the network was more broadly contagious, and not that risk was more shared. Thus, our analysis contributes to our understanding as to why defaults in US sub-prime mortgages spread quickly through the global financial system.     

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.     

The interbank network across the global financial crisis: Evidence from Italy

This study examines the effects of the global financial crisis (GFC) on interbank market connectivity using network analysis. More specifically, using data on Italian banks’ bilateral interbank positions between 1998 and 2013, we analyze the impact of the following events on each bank's network centrality: the liquidity crisis in August 2007, the collapse of Lehman Brothers in September 2008, Eurosystem's long term refinancing operations (LTROs) between 2009 and 2012, the sovereign debt crisis in July 2011, and the announcement of Outright Monetary Transactions (OMT) in 2012. The results show that the 2007 liquidity crisis and especially the collapse of Lehman Brothers are associated with a marked reduction of the relative interconnectedness of the Italian banking sector (i.e., a shift in the distribution of banks’ centrality to the left, away from the most connected bank). In the following years, the system progressively recovered its initial patterns of integration among banks, which coincided with the main Eurosystem's monetary policy interventions. However, the average outcome conceals different results across banks, depending on their characteristics and initial positions within the system.     

Network topology of the interbank market

We provide an empirical analysis of the network structure of the Austrian interbank market based on Austrian Central Bank (OeNB) data. The interbank market is interpreted as a network where banks are nodes and the claims and liabilities between banks define the links. This allows us to apply methods from general network theory. We find that the degree distributions of the interbank network follow power laws. Given this result we discuss how the network structure affects the stability of the banking system with respect to the elimination of a node in the network, i.e. the default of a single bank. Further, the interbank liability network shows a community structure that exactly mirrors the regional and sectoral organization of the current Austrian banking system. The banking network has the typical structural features found in numerous other complex real-world networks: a low clustering coefficient and a short average path length. These empirical findings are in marked contrast to the network structures that have been assumed thus far in the theoretical economic and econo-physics literature.     

Can banks default overnight? Modelling endogenous contagion on the O/N interbank market

We propose a new model of the liquidity-driven banking system focusing on overnight interbank loans. This significant branch of the interbank market is commonly neglected in the banking system modelling and systemic risk analysis. We construct a model where banks are allowed to use both the interbank and the securities markets to manage their liquidity demand and supply as driven by prudential requirements in a volatile environment. The network of interbank loans is dynamic and simulated every day. We show how the intrasystem cash fluctuations alone, without any external shocks, may lead to systemic defaults, and what may be a symptom of the self-organized criticality of the system. We also analyze the impact of different prudential regulations and market conditions on the interbank market resilience. We confirm that the central bank’s asset purchase programmes, limiting the declines in government bond prices, can successfully stabilize banks’ liquidity demands. The model can be used to analyze the interbank market impact of macroprudential tools.     

Network centrality and funding rates in the e-MID interbank market

This paper empirically investigates the role of banks’ network centrality in the interbank market on their funding rates. Specifically we analyze transaction data from the e-MID market, the only electronic interbank market in the Euro Area and US, over the period 2006–2009 that encompasses the global financial crisis. We show that interbank spreads are significantly affected by both local and global measures of connectedness. The effects of network centrality increased as the financial crisis evolved. Local measures show that having more links increases borrowing costs for borrowers and reduces premia for lenders. For global network centrality, borrowers receive a significant discount if they increase their intermediation activity and become more central, while lenders pay in general a premium (i.e. receive lower rates) for centrality. This provides evidence of the ‘too-interconnected-to-fail’ hypothesis.     

Interbank tiering and money center banks

This paper provides evidence that interbank markets are tiered rather than flat, in the sense that most banks do not lend to each other directly but through money center banks acting as intermediaries. We capture the concept of tiering by developing a core-periphery model, and devise a procedure for fitting the model to real-world networks. Using Bundesbank data on bilateral interbank exposures among 2000 banks from 1999 to 2012, we find strong evidence of tiering in the German banking system. This extent of tiering is unlikely to arise in standard random networks. Indeed, we show that bank specialization and balance sheet variables predict how banks position themselves in the interbank market. This link provides a promising avenue for understanding the formation of financial networks.     

Assessing financial contagion in the interbank market: Maximum entropy versus observed interbank lending patterns

Interbank markets allow banks to cope with specific liquidity shocks. At the same time, they may represent a channel for contagion as a bank default may spread to other banks through interbank linkages. This paper analyses how contagion propagates within the Italian interbank market using a unique data set including actual bilateral exposures. Based on the availability of information on actual bilateral exposures for all Italian banks, the results obtained by assuming the maximum entropy are compared with those reflecting the observed structure of interbank claims. The comparison indicates that, under certain circumstances, depending on the structure of the interbank linkages, the recovery rates of interbank exposures and banks’ capitalisation, the maximum entropy approach overrates the scope for contagion.     

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.     

Interbank contagion and resolution procedures: inspecting the mechanism

This paper develops a network model of a stylized banking system in which banks are connected to one another through interbank claims, which allows us to study the diffusion of default avalanches triggered by an exogenous shock under a number of different assumptions on the degree of interconnectedness, level of capitalization, liquidity buffers, the size of the interbank market and fire-sales. We expand upon the existing literature by comparing two alternative resolution mechanisms: (i) liquidations triggered by either illiquidity or insolvency-related distress implying asset sales and compensation of creditors; and (ii) a bail-in mechanism avoiding bank closure by forcing a recapitalization provided by bank creditors. Our model speaks to how contagion dynamics unravel via illiquidity-driven defaults in the first case and higher-order losses in the latter one. Within this framework, we show how the liquidity risk externality can be resolved, and we put forward a macro-criterion to assess the adequacy of the liquidity ratio introduced with Basel III.     

Interbank Credit Lines as a Channel of Contagion

This paper assesses the potential for contagion in the Swiss interbank market using new data on bilateral bank exposures as well as on credit lines. A simulation approach is applied to assess the banking system's inherent instability. Moreover, the spill-over effects of a simulated default situation in the interbank market on the liquidity and solvency of banks are measured. The main findings are, first, that there is a substantial potential for contagion. Second, the exposure as well as the credit line contagion channel are relevant for Switzerland. Third, a lender of last resort intervention could reduce spill-over effects remarkably. Finally, the structure of the interbank market has considerable impact on its resilience against spill-over effects: Centralized markets are more prone to contagion than homogenous ones. JEL classification: C81, G21. The opinions expressed herein are my own and not those of the Swiss National Bank.     

Completeness,interconnectedness and distribution of interbank exposures—a parameterized analysis of the stability of financial networks

This paper assesses the impact of a certain structure of interbank exposures on the stability of a stylized financial system. Given a certain balance sheet structure of financial institutions, a large number of valid matrices of interbank exposures is created by a random generator. Assuming a certain loss given default, domino effects are simulated. The main results are, first, that financial stability depends not only on the completeness and interconnectedness of the network, but also on the distribution of interbank exposures within the system (measured by entropy). Second, looking at random graphs, the sign of the correlation between the degree of equality of the distribution of claims and financial stability depends on the connectivity of the financial system as well as on additional parameters that affect the vulnerability of the system to interbank contagion. Third, the more concentrated the assets are within a money center model, the less stable it is. Fourth, a money center model with asset concentration among core banks is less stable than a random graph with banks of homogeneous size.     

The credit quality channel: Modeling contagion in the interbank market

We propose an algorithm to model contagion in the interbank market via what we term the “credit quality channel”. In existing models on contagion via interbank credit, external shocks to banks often spread to other banks only in case of a default. In contrast, shocks are transmitted also via asset devaluations and deteriorations in the credit quality in our algorithm. First, the probability of default (PD) of those banks directly affected by some shock increases. This increases the expected loss of the credit portfolios of the initially affected banks’ counterparties, thereby reducing the counterparties’ regulatory capital ratio. From a logistic regression we estimate the increase in the counterparties’ PD due to a reduced capital ratio. Their increased PDs in turn affect the counterparties’ counterparties, and so on. This coherent and flexible framework is applied to the bilateral interbank credit exposure of the entire German banking system in order to examine policy questions. For that purpose, we propose to measure the potential cost of contagion of a given shock scenario by the aggregated regulatory capital loss computed in our algorithm.     

Filling in the blanks: network structure and interbank contagion

The network pattern of financial linkages is important in many areas of banking and finance. Yet, bilateral linkages are often unobserved, and maximum entropy serves as the leading method for estimating counterparty exposures. This paper proposes an efficient alternative that combines information-theoretic arguments with economic incentives to produce more realistic interbank networks that preserve important characteristics of the original interbank market. The method loads the most probable links with the largest exposures consistent with the total lending and borrowing of each bank, yielding networks with minimum density. When used in a stress-testing context, the minimum-density solution overestimates contagion, whereas maximum entropy underestimates it. Using the two benchmarks side-by-side defines a useful range that bounds the cost of contagion in the true interbank network when counterparty exposures are unknown.     

Credit Risk in Interbank Networks

ABSTRACT

One of the most striking characteristics of modern financial systems is their complex interdependence, comprising a network of bilateral exposures in the interbank market, in which institutions with surplus liquidity can lend to those with a liquidity shortage. Empirical studies reveal that some interbank networks have features of scale-free networks. We explore the characteristics of financial contagion in networks whose distribution of links approaches a power law, using a model that defines banks’ balance sheets from information on network connectivity. By varying the parameters for the creation of the network, several interbank networks are built, in which the concentration of debt and credit comes from the distribution of links. The results suggest that networks that are more connected and have a high concentration of credit are more resilient to contagion than other types of networks analyzed.     

Social networks in the global banking sector

We show that banks with shared social connections partner more often in the global syndicated loan market and that central banks in the network play dominant roles in various interbank transactions, indicating that social connections facilitate business connections. However, more centralized banks in the network also contribute significantly to the global systemic risk. Moreover, we find the soft information generated by social networks is particularly valuable when potential partners operate under different accounting and regulatory standards. Finally, we show that the recent banking crisis significantly limited the positive soft information effects of social networks in the global banking system.     

Determinants of risk in the banking sector during the European Financial Crisis

Risk assessment in the banking sector has been a prominent topic in the banking literature and has gained attention especially since the recent financial crises. In particular, the European crisis, which was the first since the formation of the Eurozone, underlined a number of significant problems and increased concerns on the tail or crash risk of banks. In the present study, we seek to examine whether information asymmetry, the importance of banks in the financial system and systemic risk play significant roles in the evolution of stock crashes in the banking sector. Information asymmetry is proxied by opacity, the importance of a bank in a financial network is proxied by network centrality, and systemic risk is proxied by clustering. The research framework considers a number of regulatory, reporting and financial market factors that have also been determined to relate to stock crashes and shows that all of the above factors are related to (idiosyncratic) stock crash risk under specific conditions.     

Bank-to-bank lending channel and the transmission of bank liquidity shocks: Evidence from France

Good liquidity is essential for the banking system to function properly and supply credit to the real sector. However, several banks all over the world face large shocks to their liquidity supply due to numerous factors. This study contributes to the literature on the transmission of liquidity shocks by investigating the bank-to-bank lending behavior of French banks during the global financial crisis (2008 and 2009). In addition, we examine the factors strongly influencing the liquidity of the interbank deposits market. First, using a fixed-effects model on a sample of 85 French banks for the period from 2005 to 2010, we find that the deposits channel plays an important role in the transmission of liquidity shocks across the banking system. Second, we use difference-in-difference methodology to study the effects of liquidity shock on bank lending. Our results show that French banks reduced their bank-to-bank lending significantly during the financial crisis period. Moreover, our results suggest that the reduction could have been due to deposit activities.     

银行业改革、市场化与信贷资源的配置

鉴于我国资本市场弱法律风险和股权高度集中的基本特征,本文提出了一个分析我国银行信贷业务预期违约风险的基本框架。以此为基础,本文考察了我国的银行业改革以及市场化进程对银行信贷资源配置行为的影响。研究发现,银行配置信贷资源时,会认真考虑贷款企业的历史财务绩效和代理成本。并且,银行业改革和地区市场化进程都成功促进了银行信贷资源配置行为的商业化。本文的研究为评价银行业改革的历史进程提供了经验证据,也为进一步的努力方向提供了一些有益的线索。一方面,银行在配置其信贷资源时不仅要进一步关注贷款企业的财务绩效;另一方面,也应当致力于促使银行在确立必要报酬率时进一步关注贷款企业的代理成本。     

Interbank contagion risk in China under an ABM approach for network formation

This paper uses an agent-based model to construct an interbank network for the Chinese interbank market using a sample of 299 commercial banks from 2014 to 2019. We analyze the importance and vulnerability of banks using the DebtRank algorithm. Our results show that the Chinese interbank market bears a certain level of systemic risk, especially among lower-tiered banks. The results also show a bank is more vulnerable if it has a higher interbank lending ratio and greater financial connectivity. Meanwhile, a bank is more influential if it has a larger net worth and greater financial connectivity.