Since November 2014 I am a Senior Lecturer at the School of Economics at the University of Cape Town and with AIFMRM, the African Institute of Financial Markets and Risk Management. I am also a Policy Associate at Economics Research Southern Africa, and a Research Economist at the Research Center of Deutsche Bundesbank. Please note that this is my private website and the views presented here do not necessarily reflect the views of Bundesbank or the ESCB.
- January 2015.
"Contagious Synchronization and Endogenous Network Formation in Financial Networks" (with Christoph Aymanns, Oxford), Journal of Banking and Finance 50(1). [abstract] [paper] [video (starts at ~20min)]
When banks choose similar investment strategies the financial system becomes vulnerable to common shocks. We model a simple financial system in which banks decide about their investment strategy based on a private belief about the state of the world and a social belief formed from observing the actions of peers. Observing a larger group of peers conveys more information and thus leads to a stronger social belief. Extending the standard model of Bayesian updating in social networks, we show that the probability that banks synchronize their investment strategy on a state non-matching action critically depends on the weighting between private and social belief. This effect is alleviated when banks choose their peers endogenously in a network formation process, internalizing the externalities arising from social learning.
- February 2013.
"The Effect of Interbank Network Structure on Contagion and Common Shocks", Journal of Banking and Finance 37(7) (2013). [abstract] [latest version]
This paper proposes a dynamic multi-agent model of a banking system with central bank. Banks optimize a portfolio of risky investments and riskless excess reserves according to their risk, return, and liquidity preferences. They are linked via interbank loans and face stochastic deposit supply. Evidence is provided that the central bank stabilizes interbank markets in the short-run only. Comparing different interbank network structures, it is shown that money-center networks are more stable than random networks. Systemic risk via contagion is compared to common shocks and it is shown that both forms of systemic risk require diﬀerent optimal policy responses.
December 2015. New! "Mirror, Mirror, on the Wall, Who is the Most Central of Them All?" (with Michael Rose, University of Cape Town) [abstract] [paper]
In academia, informal collaboration is an integral element in the production of knowledge. We construct the social network of informal collaboration using acknowledgments of 2782 scholarly articles published in six journals in financial economics. We rank financial economists according to their centrality in the social network of informal collaboration and find that central commenters are not necessarily the most central or the most productive authors. We explore the determinants of high centrality rankings using detailed CV data for the most central academics. A PhD from a better ranked department is associated with a better centrality ranking. Seniority is associated with worse rankings, albeit at a decreasing rate.
August 2015. "A Network View on Interbank Liquidity" (with Silvia Gabrieli, Banque de France) [abstract] [paper]
The euro area overnight interbank market is best described as a network of lending relationships. We study liquidity reallocation in this interbank network using a novel dataset of all interbank loans settled between European banks and document a significant change in the network structure around the bankruptcy of Lehman Brothers. We show that a bank's position in the interbank network, measured by its centrality, has an economically significant effect on its liquidity access and provision. The effect is stronger for the price of liquidity than for the volume, and stronger for liquidity provision than for access to liquidity.
June 2015. "Information Contagion and Systemic Risk" (with Toni Ahnert, Bank of Canada) [abstract] [paper]
We examine the effect of ex-post information contagion on the ex-ante optimal portfolio choices of banks and the welfare losses due to joint default. Because of counterparty risk and common exposures, bad news about one bank reveals valuable information about another bank, thereby triggering information contagion. Systemic risk is defined as the ex-ante probability of joint bank default ex post. We find that information contagion increases systemic risk when banks are subject to common exposures since portfolio adjustments are small. In contrast, when banks are subject to counterparty risk, information contagion induces a large shift toward more prudential portfolios and therefore reduces systemic risk.
Work in progress:
- "Interbank Intermediation" (with Marcel Bluhm, Xiamen, and Jan-Pieter Krahnen, Goethe University Frankfurt).
- "Contagion in Coupled Trading Networks" (with Christoph Aymanns, LSE, and Ben Golub, Harvard).
- "Optimal Financial Contagion" (with Toni Ahnert, Bank of Canada, and Gideon du Rand, Stellenbosch).
- "Measuring Regulatory Complexity" (with Jean-Edouard Colliard, HEC Paris).
Interdisciplinary, Policy, and Other Publications
- "Revealing patterns of local species richness along environmental gradients with a novel network tool" (with Mara Baudena, Utrecht, Angel Sanchez, UC3M, Paloma Ruiz-Benito, Alcala, Miguel A. Rodriguez, Alcala, Miguel A. Zavala, Alcala, and Max Rietkerk, Utrecht), Nature Scientific Reports 5 (2015). [paper]
- "Seven Questions on Financial Interconnectedness" (with Camelia Minoiu, IMF), IMF Research Bulletin, (2014), March. [.pdf]
"Complex Derivatives" (with Stefano Battiston, ETH Zurich, Guido Caldarelli, IMT Lucca, Robert M. May, Oxford University, and Joseph E. Stiglitz, Columbia University), Nature Physics Vol.9, No.3, (2013). [abstract] [focus]
The intrinsic complexity of the financial derivatives market has emerged as both an incentive to engage in it, and a key source of its inherent instability. Regulators now faced with the challenge of taming this beast may find inspiration within the budding science of complex systems..
- "Systemic Risk in the Financial Sector" (with Ian Goldin, Mike Mariathasan, Oxford, and Tiffany Vogel), in: Ian Goldin and Mike Mariathasan: "The Butterfly Defect - Globalisation and Systemic Risk", Princeton University Press, (2014)
"Note on interlinkages in the South African interbank system" (with Nicola Brink), Special Note in the Financial Stability Review, South African Reserve Bank (March 2011). [abstract] [fsr]
This paper analyses the network structure of the South African overnight interbank market by employing measures from network theory. A unique data set of interbank transactions from the South African Multiple Options Settlement (SAMOS) system is used. It is shown that the South African interbank system has been largely stable and resilient over the period from March 2005 to June 2010, even in times of great distress on the international financial markets. The number of banks participating in the interbank market was approximately constant over the analysed period, as well as the high level of interconnectedness. A low average path length and high clustering coefficient indicate a high level of liquidity allocation and risk sharing in the system. Furthermore a Network Systemic Importance Index (NSII) is developed to assess the systemic importance of individual banks in South Africa. This index measures each banks size, interconnectedness and substitutability by employing network theory. It is a relative index in the sense that the systemic importance of any given bank does not only depend on the properties of the bank itself, but rather on the properties of the whole network. This approach is therefore less prone to moral hazard and can be used as a tool for macroprudential oversight in addition to microprudential supervision. The NSII addresses the cross-sectional dimension of systemic risk. It has to be stressed, however, that it gives no indication of the default probability of individual banks and has therefore be accompanied by other macroprudential tools for a full picture of systemic risk.
"Basel III and Systemic Risk Regulation - What Way Forward?", Global Financial Markets Working Paper Series 17-2011, (2011). [abstract] [paper] .
One of the most pressing questions in the aftermath of the financial crisis is how to deal with systemically important financial institutions (SIFIs). The purpose of this paper is to review the recent literature on systemic risk and evaluate the regulation proposals in the Basel III framework with respect to this literature. A number of shortcomings in the current framework are analyzed and three measures for future reform are proposed: counter-cyclical risk-weights, dynamic asset value correlation multipliers, and enhanced transparency requirements for SIFIs.
Software and Website Projects:
I am developing black_rhino, an open source financial network multi-agent simulation. You can find the most recent version (including a short tutorial) at sourceforge.
Michael Rose and I have developed a website to accompany our paper on informal collaboration in financial economics. Here you will find a ranking of financial economists based on their centrality in the network of informal collaboration. To our Website.
I am fortunate to work with a group of outstanding students and postdoctoral researchers. If your contacts are missing or outdated, it is time to get in touch again!
University of Cape Town
- Dr. Pawel Fiedor (2015-, Postdoctoral Researcher, PhD Krakow)
- Hylton Hollander, PhD (06-12/2015, Postdoctoral Researcher, Now: Lecturer Stellenbosch)
- Michael Rose (2015-, PhD Student, MSc Kiel)
- Gideon du Rand (2015-, co-advisor, PhD Student at Stellenbosch)
- Tarik Roukny (2013, intern, PhD Student ULB)
- Florian Urbschat (2013, intern, now PhD Student at TU Munich)
- Niccolo Stamboglis (2013, intern, PhD Student City University London)
- Christoph Aymanns (2013, intern, now Postdoctoral Researcher LSE)
- Dr. Raphael Flore (2014, intern, PhD Student Cologne)
- Andrea Deghi (2015, intern, PhD Student Siena)
- Dieter Wang (2015, intern, Master Student Tinbergen Institute, Amsterdam)
University of Cape Town
Useful advise: Lasse Heje Pedersen has a most useful tutorial on "How to succeed in academia" which I urge all students to read. Before starting to write your thesis or dissertation, read John Cochrane's writing tips for PhD Students (also useful for MBA Students). Those interested in applied microeconomics should also check out Jesse Shapiro's Unauthoritive Notes and Matthew Gentzkow's Code and Data for the Social Sciences: A Practitioner's Guide (with Jesse Shapiro). Details of how to give an academic talk can be found on Jonathan Shewchuk's website.
Summer Schools and Short Courses
Banking and Modern Financial Economics (University of Pretoria), 13.+14. September 2011. The course outline can be found here. The literature for the course can be found here. Some introductory material for statistics can be found in the book by Grinstead and Snell.
Contact:E-mail: email@example.com | firstname.lastname@example.org | email@example.com
Telephone: +27 21 406 1025 | Skype: co.georg | Twitter: @co_georg
Postal Address: University of Cape Town, AIFMRM, Private Bag X1, Cape Town 8000, South Africa