The Effects of Credit Risk on Dynamic Portfolio Management: A New Computational Approach

The study investigates the role of credit risk in a continuous time stochastic asset allocation model, since the traditional dynamic framework does not provide credit risk flexibility. The general model of the study extends the traditional dynamic efficiency framework by explicitly deriving the optimal value function for the infinite horizon stochastic control problem via a weighted volatility measure of market and credit risk. The model's optimal strategy was then compared to that obtained from a benchmark Markowitz-type dynamic optimization framework to determine which specification adequately reflects the optimal terminal investment returns and strategy under credit and market risks. The paper shows that an investor's optimal terminal return is lower than typically indicated under the traditional mean-variance framework during periods of elevated credit risk. Hence I conclude that, while the traditional dynamic mean-variance approach may indicate the ideal, in the presence of credit-risk it does not accurately reflect the observed optimal returns, terminal wealth and portfolio selection strategies.

Varying Injurer Costs of Care, Negligence, and Self-Selection

Standard economic models of negligence set a single standard of care to which all injurers must conform. When injurers differ in their costs of care, this leads to distortions in individual care choices. This paper derives the characteristics of a negligence rule that induces optimal care by all injurers by means of self-selection. The principal features of the rule are (1) the due standard is set at the optimal care of the lowest cost injurer, and (2) liability increases gradually rather than abruptly as care falls below this standard. The results are consistent with the gradation in liability under certain causation rules and under comparative negligence.

On Negligence Rules and Self-Selection

Economic models of negligence ordinarily involve a single standard of care that all injurers must meet to avoid liability. When injurers differ in their costs of care, however, this leads to distortions in their care choices. This paper derives the characteristics of a generalized negligence rule that induces injurers to self-select their optimal care levels. The principal features of the rule are (1) the due standard of care is maximal, and (2) liability increases gradually as injurers depart further from this standard. The results are broadly consistent with the gradation in liability under certain causation rules and under comparative negligence.