Much of the lending in modern economies is secured by some form of collateral: residential and commercial mortgages and corporate bonds are familiar examples. This paper builds an extension of general equilibrium theory that incorporates durable goods, collateralized securities and the possibility of default to argue that the reliance on collateral to secure loans and the particular collateral requirements chosen by the social planner or by the market have a profound impact on prices, allocations, market structure and the efficiency of market outcomes. These findings provide insights into housing and mortgage markets, including the sub-prime mortgage market.
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 over-investment compared to the Arrow-Debreu level. Second, we show that the introduction of naked CDS can generate under-investment with respect to the Arrow-Debreu level. Finally, we show that the introduction of naked CDS can robustly destroy competitive equilibrium.
Our paper provides a complete characterization of leverage and default in binomial economies with financial assets serving as collateral. First, our Binomial No-Default Theorem states that any equilibrium is equivalent (in real allocations and prices) to another equilibrium in which there is no default. Thus actual default is irrelevant, though the potential for default drives the equilibrium and limits borrowing. This result is valid with arbitrary preferences and endowments, arbitrary promises, many assets and consumption goods, production, and multiple periods. We also show that the no-default equilibrium would be selected if there were the slightest cost of using collateral or handling default. Second, our Binomial Leverage Theorem shows that equilibrium LTV for non-contingent debt contracts is the ratio of the worst-case return of the asset to the riskless rate of interest. Finally, our Binomial Leverage-Volatility theorem provides a precise link between leverage and volatility.
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 default. Thus actual default is irrelevant, though the potential for default drives the equilibrium and limits borrowing. This result is valid with arbitrary preferences and endowments, contingent or non-contingent promises, many assets and consumption goods, production, and multiple periods. We also show that no-default equilibria would be selected if there were the slightest cost of using collateral or handling default. Our Binomial Leverage Theorem shows that equilibrium Loan to Value (LTV) for non-contingent debt contracts is the ratio of the worst-case return of the asset to the riskless gross rate of interest. In binomial economies leverage is determined by down risk and not by volatility.
Systemic risk must include the housing market, though economists have not generally focused on it. We begin construction of an agent-based model of the housing market with individual data from Washington, DC. Twenty years of success with agent-based models of mortgage prepayments give us hope that such a model could be useful. Preliminary analysis suggests that the housing boom and bust of 1997-2007 was due in large part to changes in leverage rather than interest rates.
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 central features of the financial/macro economy, despite their complete absence (even now) from any textbooks. Finally I suggest that the Greek debt problem, and on a bigger scale, the American debt problem, can only be cured when lenders are prodded to forgive. That would be better for the borrowers but also for the lenders.
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 up during booms as leverage rises and how crises start when leverage on new loans sharply declines. Leverage data is also a crucial input for crisis management and lending facilities. Leverage at the asset level can be monitored by down payments or margin requirement or and haircuts, giving a model-free measure that can be observed directly, in contrast to other measures of systemic risk that require complex estimation. Asset leverage is a fundamental measure of systemic risk and so is important in itself, but it is also the building block out of which measures of institutional leverage and household leverage can be most accurately and informatively constructed.
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 to raise asset prices and why CDS tend to lower them. This may seem puzzling, since it implies that creating a derivative tranche in the securitization whose payoffs are identical to the CDS will raise the underlying asset price while the CDS outside the securitization lowers it. The resolution of the puzzle is that the CDS lowers the value of the underlying asset since it is equivalent to tranching cash.