Knowledge that Transforms

This paper offers a new class of models of the term structure of interest rates. We allow each instantaneous forward rate to be driven by a different stochastic shock, constrained in such a way as to keep the forward rate curve continuous. We term the process followed by the shocks to the forward curve ``stochastic strings'', and construct them as the solution to stochastic partial differential equations, that allow us to offer a variety of interesting parametrizations. The models can produce, with parsimony, any sort of correlation pattern among forward rates of different maturities. This feature makes the models consistent with any panel dataset of bond prices, not requiring the addition of error terms in econometric models. Interest rate options can easily be priced by simulation. However, options can only be perfectly hedged by trading in bonds of all maturities available.

In this article we examine the effect of the imperfect mobility of goods on international risk sharing and, through that, on the investment in risky projects, welfare, and growth. Our main result is that the welfare gain from integration of financial markets is not greatly reduced by the presence of goods market imperfections, modeled as a cost of transferring goods from one country to the other. We also find that the gain is nonmonotonic with respect to investors' risk aversion and the aggregate volatility of output growth. The policy implication to be drawn is that financial market integration is a worthwhile goal to pursue even when full goods mobility has not been achieved. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.

This article studies the security-design problem of a cash-constrained firm facing investors with diverse beliefs. Investor “rational beliefs” are modeled as varying and yet rational in the sense of Kurz (1994a). With two investors, optimal designs are similar under rational beliefs and rational expectations. With many investors, however, optimal securities under rational beliefs maximize investor differences of opinion, while under rational expectations optimal designs minimize disagreements. We demonstrate that the common practice of issuing multiple securities backed by a single asset is optimal under rational beliefs but not under rational expectations. Researching market beliefs can create substantial value for firms.

In this paper we provide a price characterization of efficient consumption bundles in multiperiod economies with market frictions. Efficient consumption bundles are those that are chosen by at least one rational agent with monotonic state-independent and risk-averse preferences and a given future endowment. Frictions include dynamic market incompleteness, proportional transaction costs, short selling costs, borrowing costs, taxes, and others. We characterize the inefficiency cost of a trading strategy -the difference between the investment it requires and the largest amount required by any rational agent to obtain the same utility level - and we propose a measure of portfolio performance based on it. We also show that the arbitrage bounds on a contingent claim to consumption cannot be tightened based on efficiency arguments without restricting preferences or endowments. We examine the efficiency of common investment strategies in economies with borrowing costs due to asymmetric information, short selling costs, or bid-ask spreads. We find that market frictions generally change and typically shrink the set of efficient investment strategies, shifting investors away from well-diversified strategies into low cost ones, and for large frictions into no trading at all. Hence we observe strategies that become inefficient with market frictions, as well as strategies that are rationalized by market frictions.

The volatility smile changed drastically around the crash of 1987, and newoption pricing models have been proposed to accommodate that change. Deterministic volatility models allowfor more flexible volatility surfaces but refrain from introducing additional risk factors. Thus, options are still redundant securities. Alternatively, stochastic models introduce additional risk factors, and options are then needed for spanning of the pricing kernel. We develop a statistical test based on this difference in spanning. Using daily S&P 500 index options data from 1986–1995, our tests suggest that both in- and out-of-the-money options are needed for spanning. The findings are inconsistent with deterministic volatility models but are consistent with stochastic models that incorporate additional priced risk factors, such as stochastic volatility, interest rates, or jumps.