This paper argues that in ebullient times equilibrium leverage and asset prices are too high; in bad times, equilibrium leverage and asset prices are too low. This is the leverage cycle. Looking at the recent American and European crises, the paper draws lessons for central banks about how to...

This paper argues that macroeconomic stability depends less on riskless interest rates than on leverage and other measures of credit conditions, like average FICO scores of borrowers. It suggests that the leverage cycle played a central role in the recent American and European financial crisis....

We prove that in competitive market economies with no insurance for idiosyncratic risks, agents will always overinvest in illiquid long term assets and underinvest in short term liquid assets. We take as our setting the seminal model of Diamond and Dybvig (1983), who first posed the question in...

Financial innovations that change how promises are collateralized can affect investment, even in the absence of any change in fundamentals. In C-models, the ability to leverage an asset always generates over-investment compared to Arrow Debreu. The introduction of CDS always leads to...

We show that financial innovations that change the collateral capacity of assets in the economy can affect investment even in the absence of any shift in utilities, productivity, or asset payoffs. First we show that the ability to leverage an asset by selling non-contingent promises can generate...

Our paper provides a complete characterization of leverage and default in binomial economies with financial assets serving as collateral. Our Binomial No-Default Theorem states that any equilibrium is equivalent (in real allocations and prices) to another equilibrium in which there is no...

We study endogenous leverage in a general equilibrium model with incomplete markets. We prove that in any binary tree leverage emerges in equilibrium at the maximum level such that VaR = 0, so there is no default in equilibrium, provided that agents get no utility from holding the collateral....

We show how the timing of financial innovation might have contributed to the mortgage boom and then to the bust of 2007-2009. We study the effect of leverage, tranching, securitization and CDS on asset prices in a general equilibrium model with collateral. We show why tranching and leverage tend...

This is the graduation speech I gave on receiving an honorary doctorate at the University of Athens Economics and Business School. I talk about my Greek family, about how I got interested in economics, and then how in the 1990s I came to think about default, collateral, and leverage as the...

We discuss how leverage can be monitored for institutions, individuals, and assets. While traditionally the interest rate has been regarded as the important feature of a loan, we argue that leverage is sometimes even more important. Monitoring leverage provides information about how risk builds...