On the existence of an implementable optimal income tax

Summary. This paper discusses the existence of an optimal income tax and distinguishes itself from the previous articles in two respects. In previous papers, the self selection condition was not necessarily consistent with the individual budget constraint. Furthermore, implementability in previous papers was implicit in individual ability, rather than individual income, as the basis of the tax function. We offer a different concept of the self selection conditions: Anti Normal Envy that is consistent with the individual budget constraint and that we show to be equivalent to the competitive equilibrium under a tax function based on income. We then establish the existence of an implementable optimal income tax.Received: 9 December 2000, Revised: 5 August 2003, JEL Classification Numbers: H21, C62, D59.Correspondence to: Jun IritaniThe authors are grateful to an anonymous referee of this journal whose suggestions were instrumental to our revision of the paper, and to Professors Takao Kataoka, Tomoyuki Kamo, Tetsuya Kishimoto, and Mototsugu Fukushige, and the members of the Kobe-Osaka Joint Seminar in Mathematical Economics, for their invaluable comments.     

On the existence of a stationary optimal stock for a multi-sector economy: A primal approach

Using a purely primal approach, we show the existence of a non-trivial stationary optimal stock for a multi-sector economy. Our result generalizes earlier work by dropping the δ-productivity assumption and by replacing the continuity hypothesis on the utility function by upper semicontinuity.     

The existence of optimal consumption policies in optimal economic growth models with nonconvex technologies

An existence theorem for a class of continuous time infinite horizon optimal growth models is developed. The underlying technology set is not assumed to be convex, instead the “slices” of the technology set corresponding to a fixed capital stock vector are assumed convex and compact in the consumption and net investment variables. This allows consideration of the case of increasing returns to scale. Existence of an optimal capital stock and consumption policy is proved directly without consideration of the underlying Hamiltonian dynamical system that arises from applying Pontryagin's maximum principle.     

On the existence of rational expectations equilibrium

We prove a theorem on the existence of rational expectations general economic equilibrium when agents condition on prices as well as on private information, and maximize the expectation of a state-dependent utility function. The key to the result is a new idealization of what it means for a set of empirical distributions to support agents' expectations. This idealization depends on the notion that agents compare their expectations with continuous versions of the random empirical distributions that are generated by the workings of the economy. The existence theorem covers all strictly concave utility functions, arbitrary distributions of the state variable, and situations in which the dimension of the state variable is large relative to the number of commodities.     

On the existence of involuntary unemployment equilibria

Conclusion We have proved the existence of equilibria implying involuntary unemployment of labour in non-competitive economies with fixed wage rate. We notice that model (II) and its extensions have not been presented as aninterpretation of Keynes' theory. We may define them as Keynesian models only in the sense that they admit involuntary unemployment equilibrium, which concept is basic to Keynes' theory. In any case, we think that these models are a first step in the development of more realistic microeconomic foundations for short-run macroeconomic theory.A first draft of this paper was presented in December 1972 at the Institute of Political Economy, Faculty of Economics and Banking, Siena University.     

On the existence of expected multi-utility representations

We prove the following facts related to the expected multi-utility representation of an affine preorder: If the prize space is not compact and if the lottery set consists of all probabilities on the prize space, standard independence and continuity axioms do not guarantee the existence of a (continuous) representation. If the prize space is σ-compact and lotteries have compact support, a representation exists. When the preorder in question is bounded, this result extends to the set of lotteries that consists of all probabilities on the prize space. For the case of monetary lotteries, the boundedness assumption in this last result can be dropped, provided that the preference relation at hand is monotone and risk-averse.     

On the existence of pure-strategy equilibria in large games

Over the years, several formalizations and existence results for games with a continuum of players have been given. These include those of Schmeidler [D. Schmeidler, Equilibrium points of nonatomic games, J. Stat. Phys. 4 (1973) 295-300], Rashid [S. Rashid, Equilibrium points of non-atomic games: Asymptotic results, Econ. Letters 12 (1983) 7-10], Mas-Colell [A. Mas-Colell, On a theorem by Schmeidler, J. Math. Econ. 13 (1984) 201-206], Khan and Sun [M. Khan, Y. Sun, Non-cooperative games on hyperfinite Loeb spaces, J. Math. Econ. 31 (1999) 455-492] and Podczeck [K. Podczeck, On purification of measure-valued maps, Econ. Theory 38 (2009) 399-418]. The level of generality of each of these existence results is typically regarded as a criterion to evaluate how appropriate is the corresponding formalization of large games.In contrast, we argue that such evaluation is pointless. In fact, we show that, in a precise sense, all the above existence results are equivalent. Thus, all of them are equally strong and therefore cannot rank the different formalizations of large games.     

On the existence of pure strategy Bertrand equilibrium

Summary The paper analyses the existence of pure strategy Nash equilibrium in price competition (or Bertrand equilibrium) in a homogeneous product market when costs are strictly convex and proves that if output is demand determined such equilibrium always exists. This paper also characterises such equilibria and shows that if firms are identical such equilibria are necessarily non-unique. However for firms with asymmetric costs it can be unique or non-unique.I am greatly indebted to Anjan Mukherji and Kunal Sengupta for this paper. I also express my profound gratitude to a referee of this journal for a very helpful set of suggestions.     

On the existence of a regulated production function

This paper examines the generalization of the regulated production function. It characterizes the set of admissible regulatory constraints that are compatible with the existence of a regulated production function in a sufficiently weak framework to encompass the usual rate-of-return constraints à la Averch and Johnson and value constraints.     

On the existence of pure-strategy perfect equilibrium in discontinuous games

We provide sufficient conditions for a (possibly) discontinuous normal-form game to possess a pure-strategy trembling-hand perfect equilibrium. We first show that compactness, continuity, and quasiconcavity of a game are too weak to warrant the existence of a pure-strategy perfect equilibrium. We then identify two classes of games for which the existence of a pure-strategy perfect equilibrium can be established: (1) the class of compact, metric, concave games satisfying upper semicontinuity of the sum of payoffs and a strengthening of payoff security; and (2) the class of compact, metric games satisfying upper semicontinuity of the sum of payoffs, strengthenings of payoff security and quasiconcavity, and a notion of local concavity and boundedness of payoff differences on certain subdomains of a player's payoff function. Various economic games illustrate our results.     

On equilibrium existence in payoff secure games

We propose a single framework for studying the existence of approximate and exact pure strategy equilibria in payoff secure games. Central to the framework is the notion of a multivalued mapping with the local intersection property. By means of the Fan-Browder collective fixed point theorem, we first show an approximate equilibrium existence theorem that covers a number of known games. Then a short proof of Reny’s (Econometrica 67:1029–1056, 1999) equilibrium existence theorem is provided for payoff secure games with metrizable strategy spaces. We also give a simple proof of Reny’s theorem in its general form for metric games in an appendix for the sake of completeness.     

On the effects of group identity in strategic environments

We examine differences in behavior between subjects interacting with a member of either the same or different identity group in both a centipede game and a series of stag hunt games. We find evidence that subjects interacting with outgroup members are more likely to behave as though best-responding to uniform randomization of the partner. We conclude that group identity not only affects player׳s social preferences, as identified in earlier research, but also affects the decision making process, independent of changes in the utility function.     

On the irrelevance of collusion in perfectly correlated environments

I study a class of agency problems that are characterized by the existence of an underlying organizational hierarchy. Specifically, I analyze a two-forked, three-tiered hierarchy. I show that when the private information of the players in the second and third tiers of the hierarchy is perfectly correlated across the two forks of the hierarchy, collusion by the players notwithstanding, the principal can always implement the full information optimum in a Bayes-Nash equilibrium.