Data and Code: Contracting Environments and Efficiency in Markets with Hidden Information: An Experiment

This paper provides the first systematic analysis of the role of contracting environments on market outcomes and efficiency in markets with hidden information using experimental methods. When markets are plagued by hidden information, competition does not necessarily ensure efficient market outcomes. This crucially depends on the nature of the hidden information: While theoretically efficiency is attained via competition under hidden information in the form of private values, severe distortions may occur under common values (such as in the classical Akerlof lemons or Rothschild-Stiglitz insurance markets). The extent of distortions in the latter case furthermore depends on the nature of competitive contracting. We present a parsimonious experimental design that serves to compare the different contracting environments, ranging from monopoly to nonexclusive competition, for both types of hidden information markets, private and common values. The degree of equilibrium play that we find is strikingly high, particularly in the complex cases of competitive common values markets. While competition ensures efficiency under private values, this is not the case under common values: distortions arise under exclusive contracting, and some agents do not trade under nonexclusive contracting.

本文首次采用实验研究方法，针对存在隐藏信息（hidden information）的市场，系统剖析契约环境对市场结果与配置效率的作用机制。当市场受困于隐藏信息时，竞争未必能保障市场实现有效率的运行结果。这一结论关键取决于隐藏信息的本质：从理论上讲，当隐藏信息以私人价值（private values）形式存在时，竞争可实现市场效率；但在共同价值（common values）场景下，市场可能出现严重的效率扭曲——例如经典的阿克洛夫柠檬市场（Akerlof lemons market）与罗斯柴尔德-斯蒂格利茨保险市场（Rothschild-Stiglitz insurance markets）。在后一类场景中，扭曲程度还取决于竞争性契约的具体属性。本文提出一种简约实验设计（parsimonious experimental design），用于对比两类隐藏信息市场（私人价值与共同价值市场）下从垄断（monopoly）到非排他性竞争（nonexclusive competition）的各类契约环境。我们观测到的均衡行为契合度极高，在竞争性共同价值市场这类复杂场景中尤为显著。尽管在私人价值场景下竞争可保障市场效率，但共同价值场景下并非如此：排他性契约（exclusive contracting）会引发效率扭曲，而非排他性契约（nonexclusive contracting）则会导致部分市场主体无法完成交易。