发表机构
Concordia University; CIREQ（康科迪亚大学; 魁北克经济学研究与发展中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出单例可达性概念，刻画匹配机制中仅报告目标对象即可获得结果的透明访问属性，并引入报告宽度度量，发现其要么为一要么无界的宽度二分法。
AI 中文摘要
匹配机制在多大程度上需要确定和报告代理人的偏好排序以获得特定对象方面有所不同。如果代理人通过某种报告能够获得的每个对象，也可以通过仅报告该对象为可接受来获得，则该机制是单例可达的（SA）。使用SA机制，一旦确定了可达对象，代理人无需对其他任何对象进行排序或报告。单例可达性在匹配理论和市场设计中识别出一个不同的维度：对可达结果的透明访问，这独立于激励、稳定性、福利或公平性。\n我们建立了SA的一般条件并推导了其战略含义。顶部提升不变性和截断不变性共同蕴含SA，而策略证明性和稳定性各自蕴含SA。相反，对策略证明、个体理性和非浪费机制的帕累托改进没有一个是SA的。特别是，对延迟接受的每个帕累托改进都违反SA。我们引入了报告宽度，它衡量为了获得一个对象可能需要报告多少个可接受对象。SA机制的报告宽度为一。\n对于一大类帕累托改进延迟接受的效率机制，报告宽度是无界的。当优先级是单调的时，具有报告诱导优先级的稳定选择具有宽度一，而在反向优先级支配下具有最大宽度。当外部选项排名固定时，排名福利最大化具有宽度一，而当其依赖于报告时具有最大宽度。这些结果揭示了一个结构性分歧，我们称之为宽度二分法：在我们分类中的所有机制和家族以及我们研究的所有结构类别中，报告宽度要么是一，要么是无界的。
英文摘要
Matching mechanisms differ in how much of an agent's preference ranking must be determined and reported to obtain a particular object. A mechanism is singleton-attainable (SA) if every object that an agent can obtain through some report can also be obtained by reporting only that object as acceptable. With an SA mechanism, once an attainable object has been identified, the agent need not rank or report any other object. Singleton-attainability identifies a distinct dimension in matching theory and market design: transparent access to attainable outcomes, separate from incentives, stability, welfare or equity. We establish general conditions for SA and derive its strategic implications. Top-lift invariance and truncation invariance together imply SA, while strategyproofness and stability each imply SA. By contrast, no Pareto improvement over a strategyproof, individually rational, and non-wasteful mechanism is SA. In particular, every Pareto improvement over Deferred Acceptance violates SA. We introduce report width, which measures how many acceptable objects may have to be reported to obtain an object. SA mechanisms have report width one. Report width is unbounded for a large class of efficient mechanisms that Pareto-improve Deferred Acceptance. Stable selection with report-induced priorities has width one when priorities are monotone and maximal width under reverse priority dominance. Rank-welfare maximization has width one when the outside-option rank is fixed and maximal width when it is report-dependent. These results reveal a structural divide, which we call the width dichotomy: across all mechanisms and families in our classification and all structural classes we study, report width is either one or unbounded.
Comments68 pages, 3 tables. JEL Classification: C78, D47
