Feasible elimination procedures in social choice: An axiomatic characterization

Feasible elimination procedures (Peleg, 1978) play a central role in constructing social choice functions which have the following property: in the associated game form, for any preference profile there exists a strong Nash equilibrium resulting in the sincere outcome. In this paper we provide an axiomatic characterization of the social choice correspondences resulting from applying feasible elimination procedures. The axioms are anonymity, Maskin monotonicity, and independent blocking. We also show that these axioms are logically independent.     

CHARACTERIZATION OF OPTIMAL STOPPING REGIONS OF AMERICAN ASIAN AND LOOKBACK OPTIONS

A general framework is developed to analyze the optimal stopping (exercise) regions of American path-dependent options with either the Asian feature or lookback feature. We examine the monotonicity properties of the option values and stopping regions with respect to the interest rate, dividend yield, and time. From the ordering properties of the values of American lookback options and American Asian options, we deduce the corresponding nesting relations between the exercise regions of these American options. We illustrate how some properties of the exercise regions of the American Asian options can be inferred from those of the American lookback options.     

基于上证50ETF期权的“定价核之谜”研究

基于上证50E T F和上证50E TF期权数据,本文经验研究了中国市场是否存在“定价核之谜”,并对“定价核之谜”与市场走势之间的关系进行了探讨。实证结果显示,中国市场存在“定价核之谜”,且“定价核之谜”与下期市场收益率呈显著负向关系、与下期市场振幅呈显著正向关系。本文首次给出了“定价核之谜”在中国金融市场存在的经验证据,并且证实了“定价核之谜”对下期市场走势具有一定的预测作用。     

Laws of scarcity for a finite game - exact bounds on estimations

Summary. A law of scarcity is that scarceness is rewarded. We demonstrate laws of scarcity for cores and approximate cores of games. Furthermore, we show that equal treatment core payoff vectors satisfy a condition of cyclic monotonicity. Our results are developed for parameterized collections of games and exact bounds on the maximum possible deviation of approximate core payoff vectors from satisfying a law of scarcity are stated in terms of the parameters describing the games. We note that the parameters can, in principle, be estimated.Received: 21 November 2002, Revised: 7 October 2003, JEL Classification Numbers: C71, C78, D41. Correspondence to: Myrna WoodersThis research was initiated in 1994 when the first author was in the IDEA Ph.D. Program of the Autonomous University of Barcelona. Support by the IBM Fund Award, the Latané Fund, the University of North Carolina Research Council, and the Warwick Centre for Public Economics is acknowledged. The second author gratefully acknowledges the support of the Direccio General dUniversitats of Catalonia, the Social Sciences and Humanities Research Council of Canada, and the Department of Economics of the Autonomous University of Barcelona. This article is dedicated to Marcel (Ket) Richter, a distinguished researcher and a wonderful teacher and mentor to his students. We are delighted to contribute our paper to this special issue of Economic Theory in his honor.     

Axiomatization of the core of assignment games

The core of assignment games is characterized by two different lists of axioms. The first list consists of Pareto optimality, consistency, pairwise monotonicity, and individual monotonicity. The second list is obtained from the first one replacing the last axiom by population monotonicity. As a corollary, individual monotonicity and population monotonicity are equivalent under the other axioms. The core is also characterized by the second list on the restricted domain in which the worth of each pair is non-negative and every reservation value is zero.     

The Neglect of Monotone Comparative Statics Methods

Monotone methods enable comparative static analysis without the restrictive assumptions of the implicit-function theorem. Ease of use and flexibility in solving comparative static and game-theory problems have made monotone methods popular in the economics literature and in graduate courses, but they are still absent from undergraduate mathematical economics courses and textbooks. In this article, the authors illustrate the generality of monotone comparative statics relative to the implicit function approach. For example, to sign the effect of a discrete policy shift on a choice variable, the marginal returns will increase with the policy parameter. They also apply monotone methods in game theory settings. As mathematical economics courses and majors gain popularity, incorporating monotone methods into curriculum and textbooks would provide a modern treatment of comparative static analysis.     

Bribe-proof rules in the division problem

The division problem consists of allocating an amount of a perfectly divisible good among a group of n agents with single-peaked preferences. A rule maps preference profiles into n shares of the amount to be allocated. A rule is bribe-proof if no group of agents can compensate one of its subgroups to misrepresent their preferences and, after an appropriate redistribution of their shares, each obtains a weakly preferred share and all agents in the misrepresenting subgroup obtain a strictly preferred share. We characterize all bribe-proof rules as the class of Pareto efficient, strategy-proof, and weakly replacement monotonic rules. This class is larger than the set of sequential allotment rules identified in Barberà et al. [Barberà, S., Jackson, M., Neme, A., 1997. Strategy-proof allotment rules. Games Econ. Behav. 18, 1–21].     

Axiomatizations of Dutta-Ray’s egalitarian solution on the domain of convex games

We show that on the domain of convex games, Dutta-Ray’s egalitarian solution is characterized by core selection, aggregate monotonicity, and bounded richness, a new property requiring that the poorest players cannot be made richer within the core. Replacing “poorest” by “poorer” allows to eliminate aggregate monotonicity. Moreover, we show that the egalitarian solution is characterized by constrained welfare egalitarianism and either bilateral consistency à la Davis and Maschler or, together with individual rationality, by bilateral consistency à la Hart and Mas-Colell.     

Virtual Nash implementation with admissible support

A social choice correspondence (SCC) is virtually implementable if it is ?$?$-close (in the probability simplex) to some (exactly) implementable correspondence [Abreu, D., Sen, A., 1991. Virtual Implementation in Nash Equilibrium. Econometrica 59, 997–1021] proved that, without restriction on the set of alternatives receiving strictly positive probability at equilibrium, every SCC is virtually implementable in Nash Equilibrium. We study virtual implementation when the supports of equilibrium lotteries are restricted. We provide a necessary and sufficient condition, imposing joint restrictions on SCCs and admissible supports. Next, we discuss how to construct supports, and we underline an important difficulty. Finally, we study virtual implementation when the support is restricted to the efficient or individually rational alternatives.     

独立学院数学改革之数学实验——Matlab平台上“四步法”研究函数的单调性与凹凸性

数学实验是高等数学改革的重要方向,借助数学软件简化数学计算,注重数学应用是数学教学的一个新动向。函数的单调性与凹凸性是高等数学中导数应用部分的一个重要内容。本文借助功能强大的数学软件Matlab,巧用计算与图形功能,提出应用导数研究函数的单调性与凹凸性的四步法,即(1)求导函数;(2)求导函数的零点;(3)画原函数与导函数图;(4)确定函数的单调性或凹凸性。该方法采用先求导函数零点再画图的顺序,确保画图区域包含导函数的零点,避免遗漏极值点或拐点,进一步通过实例系统体现该方法对函数单调性与凹凸性的可视化判定。