This paper establishes a natural and satisfying characterization of the class of collective choice rules which are acyclic and satisfy the Arrow axioms (unrestricted domain, independence of irrelevant alternatives, and the weak Pareto principle). We show that, when the number of alternatives is larger than the number of individuals, there must exist an individual who can at least some critical number of pairwise decisions. This critical number of veto pairs depends on the number of alternatives and individuals, and, as the number of alternatives increases without limit, the fraction of all pairs which some individual can veto approaches unity. We also present a global veto theorem and an axiomatic characterization of the Pareto extension rule which utilizes acyclicity rather than quasi-transitivity. ARROW [1] SHOWED that the only collective choice rules that yield weak order social preference relations and satisfy unrestricted domain, independence of irrelevant alternatives, and the weak Pareto principle are dictatorial. Gibbard [9] demonstrated that by relaxing the rationality requirement from transitivity to quasi-transitivity (i.e., transitivity of the strict preference relation) we can evade the letter though not the spirit of the Arrow dictatorship result: oligarchy, a weaker form of dictatorship, still obtains when the other three axioms are imposed. In this paper we prove a theorem parallel to those of Arrow and Gibbard for the weaker rationality requirement of acyclicity (i.e., the absence of cycles of strict preference). Since acyclicity is a necessary and sufficient condition for the existence of a nonempty set of maximal elements in every finite feasible set, there are powerful reasons for imposing it. Moreover, as we argue in Blair and Pollak [2], it is difficult to justify any stronger rationality property such as quasi-transitivity without at the same time justifying some even stronger rationality condition which implies dictatorship. Our principal result shows that, when the number of alternatives is larger than the number of individuals, there must exist an individual who can at least some critical number of pairwise decisions. (We say that individual i has a veto over the ordered pair (y, x) if he is weakly decisive for x against y-that is, if his strict preference for x over y implies weak social preference for x over y, regardless of the preferences of other individuals.) This critical number of veto pairs depends on the number of alternatives and the number of individuals. As the number of alternatives increases without limit, the fraction of all pairs that some individual can veto approaches unity. There may be more than one individual who can veto at least the critical number of pairs; indeed, it is possible for every individual to have a veto over every ordered pair of alternatives.

The right conclusion could be that there is a strong connection between the spectral components with specified periods. A possible economic interpretation could identify a strong long-term (in the sense of the specified periods) connection between both series. But that would still not allow us to say anything concerning the size and direction of the time delay between the two series. For such an analysis we would have to, at least, consider the phase angles between the components. Because of the ambivalent meaning of the phase angle (in relation to the direction and number of periods) the final answer could come only from the time domain analysis. However, the fact that only spectral components with longer periods, i.e., smaller frequencies, show coherency suggests something else: In order to influence the balance of trade the changes in the terms of trade should be durable enough. Mathematical formalization of this concept of durability would therefore be helpful. I would propose that further research be done in this respect.

JN the thirty years since Joe Bain's seminal I study (1951), many economists have attempted to determine whether or not there exists a critical level of market concentration at which a discontinuity occurs in the relation between industry concentration and profitability. In this paper we develop and test a more general model, based on organizational costs, which posits the existence of two critical levels of market concentration: one at which an existing cooperative equilibrium will break down as concentration declines, and one at which a cooperative equilibrium will become attainable as concentration increases. We show that the standard model of the critical level of concentration can be regarded as a special case of our more general model, and also that the more general model attains a statistically superior fit. In section II we briefly review some of the previous literature in this area. We develop our model in section III and specify and estimate it in sections IV and V. In sections VI and VII we summarize and interpret our results and present some policy implications of our findings.

This paper explains involuntary unemployment in terms of the response of firms to workers' group behavior. Workers' effort depends upon the norms determining a fair day's work. In order to affect those norms, firms may pay more than the market-clearing wage. Industries that pay consistently more than the market-clearing wage are primary, and those that pay only the market-clearing wage are secondary. Thus, this paper also gives a theory for division of labor markets between primary and secondary.

This paper derives an optimal job-searching strategy for workers on layoff, and an optimal recall policy for firms, when each side anticipates the other side's actions correctly. It shows that workers search for an alternative job only if the probability of recall falls below a critical level, and that firms may recall before the recovery of demand, depending on the costs of laying off and hiring workers, and the probability of losing workers on layoff. Through the use of optimal job searching and recall policies, the paper derives expressions for the duration of layoff unemployment and discusses briefly their comparative-static properties.