Diversity among banks may increase systemic risk
The problem of how to stabilize the financial system has attracted considerable attention since the global financial crisis of 2007-2009. Recently, Beal et al. (2011, gIndividual versus systemic risk and the regulator fs dilemma h, Proc Natl Acad Sci USA 108: 12647-12652) demonstrated that higher portfolio diversity among banks would reduce systemic risk by decreasing the likelihood of simultaneous defaults. Here, I show that this result is overturned once a financial network comes into play. In a networked financial system, the failure of one bank can bring about a contagion of failure. The optimality of individual risk diversification, as opposed to economy-wide risk diversification, is thus restored. I also present a new method to quantify how the diversity of bank size affects the stability of a financial system. It is shown that a higher diversity of bank size itself makes the financial system more fragile even if external risk exposure is controlled for. The main reason for this is that larger banks are more likely to become a gsuper spreader h of infectious defaults. In this situation the social cost of letting a bank fail is not uniform and depends on the size of the failing bank. This strongly implies that larger banks are systemically more important than smaller banks, and preventing large banks from being exposed to high external risks would therefore be the most effective vaccine against financial crisis.
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- Nier, Erlend & Yang, Jing & Yorulmazer, Tanju & Alentorn, Amadeo, 2007.
"Network models and financial stability,"
Journal of Economic Dynamics and Control,
Elsevier, vol. 31(6), pages 2033-2060, June.
- Iori, Giulia & De Masi, Giulia & Precup, Ovidiu Vasile & Gabbi, Giampaolo & Caldarelli, Guido, 2008.
"A network analysis of the Italian overnight money market,"
Journal of Economic Dynamics and Control,
Elsevier, vol. 32(1), pages 259-278, January.
- Iori, G. & Masi, G. D. & Precup, O. V. & Gabbi, G. & Caldarelli, G., 2005. "A network analysis of the Italian oversight money market," Working Papers 05/05, Department of Economics, City University London.
- Gai, Prasanna & Kapadia, Sujit, 2010. "Contagion in financial networks," Bank of England working papers 383, Bank of England.
- Larry Eisenberg & Thomas H. Noe, 2001. "Systemic Risk in Financial Systems," Management Science, INFORMS, vol. 47(2), pages 236-249, February.
- Helmut Elsinger & Alfred Lehar & Martin Summer, 2006.
"Risk Assessment for Banking Systems,"
INFORMS, vol. 52(9), pages 1301-1314, September.
- Upper, Christian, 2011. "Simulation methods to assess the danger of contagion in interbank markets," Journal of Financial Stability, Elsevier, vol. 7(3), pages 111-125, August.
- Gai, Prasanna & Haldane, Andrew & Kapadia, Sujit, 2011. "Complexity, concentration and contagion," Journal of Monetary Economics, Elsevier, vol. 58(5), pages 453-470.
- Lenzu, Simone & Tedeschi, Gabriele, 2012.
"Systemic risk on different interbank network topologies,"
Physica A: Statistical Mechanics and its Applications,
Elsevier, vol. 391(18), pages 4331-4341.
- Simone LENZU & Gabriele TEDESCHI, 2012. "Systemic risk on different interbank network topologies," Working Papers 375, Universita' Politecnica delle Marche (I), Dipartimento di Scienze Economiche e Sociali.
- F. Kyriakopoulos & S. Thurner & C. Puhr & S. W. Schmitz, 2009. "Network and eigenvalue analysis of financial transaction networks," The European Physical Journal B: Condensed Matter and Complex Systems, Springer;EDP Sciences, vol. 71(4), pages 523-531, October.
- Xavier Gabaix, 1999. "Zipf's Law for Cities: An Explanation," The Quarterly Journal of Economics, Oxford University Press, vol. 114(3), pages 739-767.
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