Knowledge that Transforms

Value at risk (VaR) and conditional value at risk (CVaR) are frequently used as risk measures in risk management. Compared to VaR, CVaR is attractive since it is a coherent risk measure. We analyze the problem of computing the optimal VaR and CVaR portfolios. We illustrate that VaR and CVaR minimization problems for derivatives portfolios are typically ill-posed. We propose to include cost as an additional preference criterion for the CVaR optimization problem. We demonstrate that, with the addition of a proportional cost, it is possible to compute an optimal CVaR derivative investment portfolio with significantly fewer instruments and comparable CVaR and VaR. A computational method based on a smoothing technique is proposed to solve a simulation based CVaR optimization problem efficiently. Comparison is made with the linear programming approach for solving the simulation based CVaR optimization problem.

This paper develops a computational approach to determining the moments of the distribution of the error in a dynamic hedging or payoff replication strategy under discrete trading. In particular, an algorithm is developed for portfolio affine trading strategies, which lead to portfolio dynamics that are affine in the portfolio variable. This structure can be exploited in the computation of moments of the hedging error of such a strategy, leading to a lattice based backward recursion similar in nature to lattice based pricing techniques, but not requiring the portfolio variable. We use this algorithm to analyze the performance of portfolio affine hedging strategies under discrete trading through the moments of the hedging error.

Recent evidence demonstrates that corporate payout policy has shifted from the nearly exclusive use of dividend payout to the inclusion of stock repurchase, primarily through open markets. This trend has been attributed to the tax advantages associated with repurchase relative to dividends. In this paper, we introduce personal taxation and stock repurchase to reexamine the relation between returns and the bid–ask spread. Our model provides insight into the nature of this relation. Tests performed using NYSE, AMEX, and NASDAQ data provide empirical support of our theoretical conclusions. We conclude that the firm’s choice of payout policy influences the relation between returns and spreads.

In this paper we discuss the interaction of default risk and liquidity risk on pricing financial contracts. We show that two risks are almost indistinguishable if the underlying contract has non-negative values; however, if it can take both positive and negative values then these two risks demand different risk premiums depending on their loss rates and distributions. We discuss a structural default model and a discrete time default model with exponentially distributed liquidity shocks. We show that short-term yield spreads are dominated by liquidity risk rather than credit risk. We suggest a two-stage procedure to calibrate the model with one scalar optimization problem and one linear programming problem.

This paper examines the growth of electronic communication networks (ECNs) and their competitive impact on the Nasdaq. We find that the development of these alternative trading platforms is associated with tighter quoted, effective, and relative bid–ask spreads, greater depths, and less concentrated markets. Further, our results show that an increase in ECN trading may have caused some traditional market makers (wholesaler and national retail dealers) to exit the market for market making. Overall, our results suggest that ECNs provide a source of competition to traditional Nasdaq dealers.

The developed world exhibits substantial but poorly understood differences in the efficiency and quality of low value payment services. This paper compares payment arrangements in the UK, Norway, Sweden, and Finland, and discusses the impact of network effects on incentives to adopt new payments technology. A model is presented, in which private benefits for investment in shared inter-bank payments infrastructure are weak. In contrast, due to ‘account externalities’, there are strong incentives for investment in intra-bank payment systems. These two features, distinguishing bank payments from other network industries, can help explain some of the observed cross-country differences in payment arrangements.

Magnetic stripe cards are in common use for electronic payments and cash withdrawal. Reported incidents document that criminals easily pickpocket cards or skim them by swiping them through additional card readers. Personal identification numbers (PINs) are obtained by shoulder surfing, through the use of mirrors or concealed miniature cameras. Both elements, the PIN and the card, are generally sufficient to give the criminal full access to the victim’s account. In this paper, we present alternative PIN entry methods to which we refer as cognitive trapdoor games. These methods make it significantly harder for a criminal to obtain PINs even if he fully observes the entire input and output of a PIN entry procedure. We also introduce the idea of probabilistic cognitive trapdoor games, which offer resilience to shoulder surfing even if the criminal records a PIN entry procedure with a camera. We studied the security as well as the usability of our methods. The result support the hypothesis that our primary mechanism strikes a balance between security and usability that is of practical value. In this article, we give a detailed account of our mechanisms and their evaluation.

This paper documents nonlinear cross-sectional dependence in the term structure of US-Treasury yields and points out risk management implications. The analysis is based on a Kalman filter estimation of a two-factor affine model which specifies the yield curve dynamics. We then apply a broad class of copula functions for modeling dependence in factors spanning the yield curve. Our sample of monthly yields in the 1982–2001 period provides evidence of upper tail dependence in yield innovations; i.e., large positive interest rate shocks tend to occur under increased dependence. In contrast, the best-fitting copula model coincides with zero lower tail dependence. This asymmetry has substantial risk management implications. We give an example in estimating bond portfolio loss quantiles and report the biases which result from an application of the normal dependence model.

We analyze the optimal hedging policy of a firm that has flexibility in the timing of investment. Conventional wisdom suggests that hedging adds value by alleviating the under-investment problem associated with capital market frictions. However, our model shows that hedging also adds value by allowing investment to be delayed in circumstances where the same frictions would cause it to commence prematurely. Thus, hedging can have the paradoxical effect of reducing investment. We also show that greater timing flexibility increases the optimal quantity of hedging, but has a non-monotonic effect on the additional value created by hedging. These results may help explain the empirical findings that investment rates do not differ between hedgers and non-hedgers, and that hedging propensities do not depend on standard measures of growth opportunities.

On April 1, 2002, the Japanese government lifted a blanket guarantee of all deposits and began limiting the coverage of time deposits. This paper uses this deposit insurance reform as a natural experiment to investigate the relationship between deposit insurance coverage and market discipline. I find that the reform raised the sensitivity of interest rates on deposits, and that of deposit quantity to default risk. In addition, the interest rate differentials between partially insured large time deposits and fully insured ordinary deposits increased for risky banks. These results suggest that the deposit insurance reform enhanced market discipline in Japan. I also find, however, that too-big-to-fail (TBTF) policy became a more important determinant of interest rates and deposit allocation after the reform, thereby partially offsetting the positive effects of the deposit insurance reform on overall market discipline.