A structural model of interbank network formation and contagion, with Patrick Coen (Toulouse School of Economics)
The interbank network, in which banks compete with each other to supply and demand financial products, creates surplus but may also result in risk propagation. We examine this trade-off by setting out a model in which banks form interbank network links endogenously, taking into account the effect of links on default risk. We estimate this model based on novel, granular data on aggregate exposures between banks. We find that the decentralised interbank network is not efficient, primarily because banks do not fully internalise a network externality in which their interbank links affect the default risk of other banks. A social planner would be able to increase surplus on the interbank network by 13% without increasing mean bank default risk or decrease mean bank default risk by 4% without decreasing interbank surplus. We propose two novel regulatory interventions (caps on aggregate exposures and pairwise capital requirements) that result in efficiency gains.
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Price discrimination and mortgage choice, with Anil Kashyap (Chicago Booth) and May Rostom (Bank of England)
We characterize the large number of mortgage offers for which people qualify. Almost no one picks the cheapest option, nonetheless the one selected is not usually much more expensive. A few borrowers make very expensive choices. These big mistakes are most common when the menu they face has many expensive options, and are most likely for high loan-to-value and loan-to-income borrowers. Young people and first-time buyers are more mistake-prone. The dispersion in the mortgage menu is consistent with banks attempting to price discriminate for some borrowers who might pick poorly while competing for others who might shop more effectively.
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