Dark Markets,by Darrell Duffie

This paper develops a method for selecting and analysing stress scenarios for financial risk assessment, with particular emphasis on identifying sensible combinations of stresses to multiple factors. We focus primarily on reverse stress testing – finding the most likely scenarios leading to losses exceeding a given threshold. We approach this problem using a nonparametric empirical likelihood estimator of the conditional mean of the underlying market factors given large losses. We then scale confidence regions for the conditional mean by a coefficient that depends on the tails of the market factors to estimate the most likely loss scenarios. We provide rigorous justification for the confidence regions and the scaling procedure when the joint distribution of the market factors and portfolio loss is elliptically contoured. We explicitly characterize the impact of the heaviness of the tails of the distribution, contrasting a broad spectrum of cases including exponential tails and regularly varying tails. The key to this analysis lies in the asymptotics of the conditional variances and covariances in extremes. These results also lead to asymptotics for marginal expected shortfall and the corresponding variance, conditional on a market stress; we combine these results with empirical likelihood significance tests of systemic risk rankings based on marginal expected shortfall in stress scenarios.     

Corporate Bond Valuation and Hedging with Stochastic Interest Rates and Endogenous Bankruptcy

This paper analyzes corporate bond valuation and optimal calland default rules when interest rates and firm value are stochastic.It then uses the results to explain the dynamics of hedging.Bankruptcy rules are important determinants of corporate bondsensitivity to interest rates and firm value. Although endogenousand exogenous bankruptcy models can be calibrated to producethe same prices, they can have very different hedging implications.We show that empirical results on the relation between corporatespreads and Treasury rates provide evidence on duration, andwe find that the endogenous model explains the empirical patternsbetter than do typical exogenous models.     

A model of liquidity hoarding and term premia in inter-bank markets

Financial crises are associated with reduced volumes and extreme levels of rates for term inter-bank loans, reflected in one-month and three-month LIBOR. We explain such stress by modeling leveraged banks' precautionary demand for liquidity. Asset shocks impair a bank's ability to roll over debt because of agency problems associated with high leverage. In turn, banks hoard liquidity and decrease term lending as their rollover risk increases over the term of the loan. High levels of short-term leverage and illiquidity of assets lead to low volumes and high rates for term borrowing. In extremis, inter-bank markets can completely freeze.     

A theory of systemic risk and design of prudential bank regulation

Systemic risk is modeled as the endogenously chosen correlation of returns on assets held by banks. The limited liability of banks and the presence of a negative externality of one bank’s failure on the health of other banks give rise to a systemic risk-shifting incentive where all banks undertake correlated investments, thereby increasing economy-wide aggregate risk. Regulatory mechanisms such as bank closure policy and capital adequacy requirements that are commonly based only on a bank’s own risk fail to mitigate aggregate risk-shifting incentives, and can, in fact, accentuate systemic risk. Prudential regulation is shown to operate at a collective level, regulating each bank as a function of both its joint (correlated) risk with other banks as well as its individual (bank-specific) risk.     

Delays and partial agreements in multi-issue bargaining

We model a situation in which two players bargain over two pies, one of which can only be consumed starting at a future date. Suppose the players value the pies asymmetrically: one player values the existing pie more than the future one, while the other player has the opposite valuation. We show that players may consume only a fraction of the existing pie in the first period, and then consume the remainder of it, along with the second pie, at the date at which the second pie becomes available. Thus, our model features a special form of bargaining delay, in which agreements take place in multiple stages. Such partial agreements arise when players are patient enough, when they expect the second pie to become available soon, and when the asymmetry in their valuations is large enough.     

Securitization without risk transfer

We analyze asset-backed commercial paper conduits, which experienced a shadow-banking run and played a central role in the early phase of the financial crisis of 2007–2009. We document that commercial banks set up conduits to securitize assets worth $1.3 trillion while insuring the newly securitized assets using explicit guarantees. We show that regulatory arbitrage was an important motive behind setting up conduits. In particular, the guarantees were structured so as to reduce regulatory capital requirements, more so by banks with less capital, and while still providing recourse to bank balance sheets for outside investors. Consistent with such recourse, we find that conduits provided little risk transfer during the run, as losses from conduits remained with banks instead of outside investors and banks with more exposure to conduits had lower stock returns.