Abstract: This paper examines time-series and cross-country variations in default risk co-dependence in the global banking system. The authors construct a default risk measure for all publicly traded banks using the Merton contingent claim model, and examine the evolution of the correlation structure of default risk for more than 1,800 banks in more than 60 countries. They find that there has been a significant increase in default risk co-dependence over the three-year period leading to the financial crisis. They also find that countries that are more integrated, and that have liberalized financial systems and weak banking supervision, have higher co-dependence in their banking sector. The results support an increase in scope for international supervisory co-operation, as well as capital charges for "too-connected-to-fail" institutions that can impose significant externalities.
The last decade has seen a tremendous transformation in the global financial sector. Globalization, innovations in communications technology and de-regulation have led to significant growth of financial institutions around the world. These trends had positive economic benefits and have led to increased productivity, increased capital flows, lower borrowing costs, and better price discovery and risk diversification. But the same trends have also led to greater linkages across financial institutions around the world as well as an increase in exposure of these institutions to common sources of risk. The recent financial crisis has demonstrated that financial institutions around the world are highly inter-connected and that vulnerabilities in one market can easily spread to other markets outside of national boundaries.
In this paper we examine whether the global trends described above have led to an increase in co-dependence in default risk of commercial banks around the world. The growing expansion of financial institutions beyond national boundaries over the past decade has resulted in these institutions competing in increasingly similar markets, exposing them to common sources of market and credit risk. During the same period, rapid development of new financial instruments has created new channels of inter-dependency across these institutions. Both increased interconnections and common exposure to risk makes the banking sector more vulnerable to economic, liquidity and information shocks. There is substantial theoretical literature that models the various channels through which such shocks can culminate in a systemic banking crisis (see for instance Bhattacharya and Gale 1987, Allen and Gale 2000, Diamond and Rajan 2005; and focusing on the recent crisis, Brunnermeier 2009, Danielsson, Shin, and Zigrand 2009, Battiston et al. 2009 among others.) To examine whether the global banking sector has become more interdependent and more fragile to shocks, we construct a default risk measure for all publicly traded banks using the Merton (1974) contingent claim model. We compute weekly time series of default probabilities for over 1,800 banks in over 60 countries and examine the evolution of the correlation structure of default risk over the 1998 – 2010 time period.
Our empirical findings show that there has been a substantial increase in co-dependence in default risk of publicly traded banks starting around the beginning of 2004 leading up to the global financial crisis starting in the summer of 2007. Although we observe an overall trend towards convergence in default risk globally, this trend has been much stronger for North American and European banks. We also find that increase in co-dependence has been higher for banks that are larger (with greater than 50 billion in assets). We also examine variation in co-dependence across countries. We find that countries that are more integrated, have liberalized financial systems and weak banking supervision have higher co-dependence in their banking sector.
Increased co-dependence in credit risk in the banking sector has important implications for capital regulations. In the aftermath of the sub-prime crisis of 2007/08, there has been renewed interest in macro-prudential regulation and supervision of the financial system. There has also been a growing consensus to adjust capital requirements to better reflect an individual bank‟s contribution to the risk of the financial system as a whole (Brunnermeier, Crockett, Goodhart, Persaud, and Shin 2009, Financial Stability Forum 2009a, 2009b). Recently a number of papers have tried to measure and quantify systemic risk inherent in the global banking sector. Adrian and Brunnermeier (2009), Huang, Zhou, and Zhou (2009), Chan-Lau and Gravelle (2005), Avesani et al. (2006), and Elsinger and Lehar (2008), use a portfolio credit risk approach to compute the contribution of an individual bank to the risk of a portfolio of banks. Our paper is related to this strand of literature, but our focus is not on quantifying systemic risk of large financial institutions but rather to examine time series trends for a large cross-section of banks. A number of papers have examined the correlation structure of equity returns of a subsample of banks. De Nicolo and Kwast (2002) find rising correlations between bank stock returns in the U.S. from 1988 and 1999. Schuler (2002) find similar results for Europe using a sample from 1980 to 2001. Hawkesby, Marsh and Stevens (2005) analyze co-movements in equity returns for a set of US and European large complex financial institutions using several statistical techniques and find a high degree of commonality. This paper is also related to the literature that studies contagion in financial markets (see among others Forbes and Rigobon 2002, Kee-Hong Bae and Stulz 2003) and also the literature that examines the impact of globalization on convergence of asset prices (Bekeart and Wang 2009, Longin and Solnik 1995, Bekaert and Harvey 2000, and Bekaert, Hodrick and Zhang 2009).
This paper differs from the existing literature in three respects. First, our empirical analyses cast a wider net than the existing literature which focuses only in a particular region or a country and covers a shorter time period. Second we examine time series trends in co-dependence and test for structural changes over time. Finally, we examine cross-country differences in co-dependence and link the differences to measures of financial and economic openness and regulatory frameworks in different countries.
Policymakers may be able to draw important implications from our analysis. Co-dependence in bank default risk has important consequences for systemic stability. We find increasing co-dependence in banks located in different national jurisdictions. Although we do find that strong banking supervision tends to reduce co-dependence in a given country, our results call for banking supervisory co-operation at a global level. This is especially true for larger banks which have grown more interconnected over the past decade.