Systemic Risk and the Refinancing Ratchet Effect

62 Pages Posted: 15 Sep 2009 Last revised: 5 Feb 2012

Amir Khandani

Massachusetts Institute of Technology (MIT)

Andrew W. Lo

Massachusetts Institute of Technology (MIT) - Sloan School of Management; National Bureau of Economic Research (NBER); Massachusetts Institute of Technology (MIT) - Computer Science and Artificial Intelligence Laboratory (CSAIL)

Robert C. Merton

Massachusetts Institute of Technology (MIT) - Sloan School of Management; National Bureau of Economic Research (NBER); Harvard Business School - Finance Unit

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Date Written: September 15, 2009

Abstract

The confluence of three trends in the U.S. residential housing market - rising home prices, declining interest rates, and near-frictionless refinancing opportunities - led to vastly increased systemic risk in the financial system. Individually, each of these trends is benign, but when they occur simultaneously, as they did over the past decade, they impose an unintentional synchronization of homeowner leverage. This synchronization, coupled with the indivisibility of residential real estate that prevents homeowners from deleveraging when property values decline and homeowner equity deteriorates, conspire to create a “ratchet” effect in which homeowner leverage is maintained or increased during good times without the ability to decrease leverage during bad times. If refinancing-facilitated homeowner-equity extraction is sufficiently widespread - as it was during the years leading up to the peak of the U.S. residential real-estate market - the inadvertent coordination of leverage during a market rise implies higher correlation of defaults during a market drop. To measure the systemic impact of this ratchet effect, we simulate the U.S. housing market with and without equity extractions, and estimate the losses absorbed by mortgage lenders by valuing the embedded put-option in non-recourse mortgages. Our simulations generate loss estimates of $1.5 trillion from June 2006 to December 2008 under historical market conditions, compared to simulated losses of $280 billion in the absence of equity extractions.

Keywords: Systemic Risk, Financial Crisis, Household Finance, Real Estate, Subprime

JEL Classification: G01, G12, G13, G18, G21, E17, E27, E37, E47, R21, R38

Suggested Citation

Khandani, Amir and Lo, Andrew W. and Merton, Robert C., Systemic Risk and the Refinancing Ratchet Effect (September 15, 2009). MIT Sloan Research Paper No. 4750-09; Harvard Business School Finance Working Paper No. 1472892. Available at SSRN: https://ssrn.com/abstract=1472892 or http://dx.doi.org/10.2139/ssrn.1472892

Amir E. Khandani

Massachusetts Institute of Technology (MIT) ( email )

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Andrew W. Lo (Contact Author)

Massachusetts Institute of Technology (MIT) - Sloan School of Management ( email )

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National Bureau of Economic Research (NBER) ( email )

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Massachusetts Institute of Technology (MIT) - Computer Science and Artificial Intelligence Laboratory (CSAIL)

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Robert C. Merton

Massachusetts Institute of Technology (MIT) - Sloan School of Management ( email )

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National Bureau of Economic Research (NBER)

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Harvard Business School - Finance Unit ( email )

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