[A choice function C on X identifies, for each subset Y of X, a set C(Y) of "best" alternatives in Y. A. computationally viable choice function is one for which a member of the choice set C(Y) can be located by a computational procedure which does not waste time, generates reasonably satisfactory intermediate alternatives, and adjusts easily as new alternatives become available. Computational viability is defined precisely and the class of computationally viable choice functions is neatly characterized. In addition, the various types of binary choice functions are distinguished in terms of computational criteria.]

THIS PAPER IS A THEORETICAL examination of the stochastic behavior of equilibrium asset prices in a one-good, pure exchange economy with identical consumers. The single good in this economy is (costlessly) produced in a number of different productive units; an asset is a claim to all or part of the output of one of these units. Productivity in each unit fluctuates stochastically through time, so that equilibrium asset prices will fluctuate as well. Our objective will be to understand the relationship between these exogenously determined productivity changes and market determined movements in asset prices. Most of our attention will be focused on the derivation and application of a functional equation in the vector of equilibrium asset prices, which is solved for price as a function of the physical state of the economy. This equation is a generalization of the Martingale property of stochastic price sequences, which serves in practice as the defining characteristic of market efficiency, as that term is used by Fama [7] and others. The model thus serves as a simple context for examining the conditions under which a price series' failure to possess the Martingale property can be viewed as evidence of non-competitive or irrational behavior. The analysis is conducted under the assumption that, in Fama's terms, prices fully reflect all available an hypothesis which Muth [13] had earlier termed rationality of expectations. As Muth made clear, this hypothesis (like utility maximization) is not behavioral: it does not describe the way agents think about their environment, how they learn, process information, and so forth. It is rather a property likely to be (approximately) possessed by the outcome of this unspecified process of learning and adapting. One would feel more comfortable, then, with rational expectations equilibria if these equilibria were accompanied by some form of stability theory which illuminated the forces which move an economy toward equilibrium. The present paper also offers a convenient context for discussing this issue. The conclusions of this paper with respect to the Martingale property precisely replicate those reached earlier by LeRoy (in [10] and [11]), and not surprisingly, since the economic reasoning in [10] and the present paper is the same. The

[A gap is filled in a proof of a central limit theorem, for regression in a time series context, which has been used in some econometric theory.]

[Very often, an index number used in an economic model has been constructed in two or more stages. If the two stage procedure gives the same answer as a single stage procedure, then Vartia calls the index number formula "consistent in aggregation." Paasche and Laspeyres indexes have this consistency in aggregation property, but these index number formulae are consistent only with very restrictive functional forms for the underlying aggregator (i.e., utility or production) function. The present paper shows that the class of superlative index number formulae has an approximate consistency in aggregation property, where a superlative index number formula is one which is consistent with a flexible functional form for the underlying aggregator function. The paper also contains some empirical examples which both illustrate the main theorem and also indicate that the chain principle for constructing index numbers is preferable to the fixed base method. Finally, the paper proves some theorems about the class of pseudo-superlative index numbers.]

An examination of two types of simple forecasting models using preliminary data compares the merits of optiml versus traditional predictors and indicates the relationship of delay in the availability of data revisions to forecasting accuracy. The Kalman filter approach is used in the first model, based on the optimal use of data containing errors in forecasting. Several suboptimal predictors, which ignore preliminary data, treat it as error-free, or adjust for bias and serial correlation, are then compared. A significant improvement in accuracy is demonstrated with the optimal use of forecasting models. Whether accuracy will improve with more complex models is not yet known. 10 references.

Recently, the appropriateness of the weighted average cost of capital for making decisions on capital structure and the selection of projects has been seriously questioned. Arditti [1] showed that when project lives were finite, the weighted average cost of capital was not appropriate for valuing the firm. Beranek [2] demonstrates that when the objective is shareholder wealth maximization, the appropriate discount rate for capital budgeting decisions for finite lived projects n > 1 is not the traditional weighted average cost of capital.

This study presents theory and some exploratory empirical work on several separate strands of monetarism in an international context and reports the results of tests of the two interrelated hypotheses: (a) the United States' monetary expansion was responsible forthe exportation of inflation to the rest of the world during the period of generally fixed exchange rates that lasted from the end of World War II until August 1971 (followed by the Smithsonian revaluations and generalized floating in March 1973), and (b) foreign nations could not control their money supplies, even in the short run, to prevent importing inflation. Succinctly stated, the monetarist approach to macroeconomic phenomena holds that money is preeminent in determining the short-run shocks to real output and the long-run price level of an economy. However, received theory is simply not clear as to whose money is most important in an international context. Is it the domestic money stock which is kept relativelyindependent of foreign forces under fixed exchange rates through astute central bank policy, at least in the short run? Is it the rest of the world money stock which, under fixed exchange rates, is a close substitute for domestic money? Or is it the money stock of the so-called world's banker, the United States, which drives foreign economies? We address these issues and others in our empirical analysis.

Since call option trading started on the Chicago Board Options Exchange (CBOE) in April 1973, the interest shown by both the investment and academic communities has grown as rapidly as the volume of option trading. In May 1973, the first full month of trading on the CBOE, a total of 34,599 contracts were traded; during 1976, the monthly volume reached 1.5 million contracts on the CBOE and 800,000 contracts on the American Stock Exchange. At present the New York Stock Exchange and certain regional exchanges are evaluating the feasibility of adapting option trading for their respective exchanges.

Jonathan E. Ingersoll, Jr., Jeffrey Skelton, Roman L. Weil, Duration Forty Years Later, The Journal of Financial and Quantitative Analysis, Vol. 13, No. 4, Proceedings of Thirteenth Annual Conference of the Western Finance Association, June 20-26, 1978 (Nov., 1978), pp. 627-650

Reviews the book "Introductory Accounting," by Charles F. Grant.