Knowledge that Transforms

A number of recent papers have reported evidence that stock prices are more volatile than is consistent with efficient markets. We argue that the excess volatility tests address a definition of efficient markets that makes an extreme information assumption. We go on to test a weaker definition of efficient markets, due to Jensen (1978). We show the existence of a profitable trading rule that earns a significantly higher rate of return than a buy-and-hold strategy, and so conclude that stock prices are too volatile, even when judged by this weaker definition.

Previous research has separately addressed the problem of estimating risk in the presence of infrequent trading and the problem of estimating quality-adjusted returns in markets with quality variation in the observed price series. This paper simultaneously addresses both problems by applying a signal extraction method for unequally spaced data to decompose the observed price series with varying times between transactions into a quality-adjusted, permanent component (which would be observable in the absence of quality variation) plus a stationary, transitory quality variation component. Stamp auction transaction prices provide an application. Auction quality grading is treated in a manner analogous to bond ratings. Almost all of the observed variance is attributed to the auction quality variation. The observed auction returns and stock index returns are not well related.

Current literature stresses that efficient funds do not exist when asset returns are continuously distributed. This paper shows that the existence of efficient funds can be restored if security returns are generated by a linear factor model.

In a recent study, Tinic and West (1986) empirically reexamine the risk-return relationship posited by the traditional mean-variance CAPM. They find a positive nonlinear relationship between risk and return, except during January when the market rewards bearing nonsystematic risk. This study examines the hypothesis that nonnormality of return distributions may account for some of these anomalous results. We compare Shalit and Yitzhaki's (1984) mean-extended Gini CAPM—an equilibrium asset pricing relation that is independent of the form of the underlying asset distribution—with the traditional CAPM. Our results indicate that the nonlinear risk-return relationship and the size and January effects are robust to nonnormality of return distributions.

Recent papers by Lamoureux and Poon (1987) and Brennan and Copeland (1988) document a significant permanent increase in average beta subsequent to stock split ex-dates. This paper demonstrates that the shift in estimated beta following ex-dates decays as the measurement interval is lengthened. There is no statistically significant difference between pre- and post-split betas using the Scholes-Williams (1977) estimator and weekly return data, or using monthly returns. We conclude that Lamoureux and Poon's and Brennan and Copeland's results can be attributed to a bias created by using too short a return measurement interval to estimate beta.

This paper identifies five universal currency hedge ratio (UHR) definitions. These are hedge positions in foreign bonds, stated as a fraction of national or global equity portfolios, that are the same for all investors, regardless of nationality. The first three involve the total demand for foreign bonds and depend on equities not being held for hedging purposes. The last two are associated with variance-minimizing regression hedges. These hold, in general, but are designed exclusively for hedging other traded asset positions. Jensen's inequality makes the choice of measurement currency irrelevant and makes the HRs universal without affecting their values.

This paper provides closed form solutions for futures and European futures options on pure discount bonds under the Ornstein-Uhlenbeck (normal) process. A significant difference between Black's model (1976) and the model in this paper for futures options is discussed.

This paper provides a closed form solution for the value of a multiple claim insurance contract that is subject to a deductible amount and/or an upper limit on claims. The solution is a time integral of European option prices. The model provides three important insights. First, systematic risk in insurance policies is altered in the presence of deductibles and maximum indemnity levels. Second, idiosyncratic risk affects policy valuation and the required rates of return on underwriting portfolios. Finally, contrary to traditional actuarial intuition, changes in the risk-free interest rate may either increase or reduce policy values.

This paper tests the null hypothesis of no difference in the probability of a trade occurring at the ask using a new database containing intraday bid-ask quotes and transaction prices on both U.S. and Canadian Exchanges. We use LOGIT analysis to test the hypothesis across days of the week, price-stratified portfolios, and times of the day. We find systematic patterns in the probability of a trade at the ask resembling previously documented returns anomalies and conclude that the findings of previous weekend and intraday returns studies may be overstated. The significance of this conclusion substantially increases as one moves from the use of interday to intraday data.

This paper examines a dynamic production economy with incomplete information and shows that the set of myopic preferences, those that induce myopic decisions, depends on the representation of the information flow. For example, logarithmic preferences are nonmyopic when some of the economic state variables are unobservable. The analysis offers a broader definition of myopic behavior, termed “generalized myopia, ” which is independent of the representation of the information flow. Allowing for any smooth concave utility function, logarithmic preferences endogenously emerge as necessary for generalized myopia in incomplete information economies; and when combined with restrictions on the information structure, they become sufficient.