简单而接近最优的市场中介机制
Simple and Near-Optimal Mechanisms For Market Intermediation
摘要：
互联网经济中普遍存在的市场结构由通过平台（如亚马逊或eBay）连接的买家和卖家组成，该平台充当中介并分享每笔交易的收入。虽然在这种情况下使中间人的利润最大化的最佳机制可能相当复杂，但实际上观察到的机制通常要简单得多，例如，将仿射函数应用于交易价格作为中介费用。Loertscher和Niedermayer [2007]开始研究双边市场中的这种费用设定机制，我们通过解决仿射费用表何时近似最优的问题来继续这项研究。一方面，我们的工作提供了非平凡的充分条件，在买方（即线性的边际收入函数，或MHR属性的价值和价值减去成本分布）下，仿射费用表可以获得一个常数部分的中介的最优利润的所有卖方分布。另一方面，我们补充我们的结果表明，适当的仿射费用设置机制（例如，在eBay和亚马逊销售计划中使用的）是无法提取最坏情况下的卖家分布的最佳利润的一个恒定的部分。作为子公司的结果，我们还表明，在上述条件下，最大盈余和最大收入之间存在一个恒定的差距。我们提出的大多数机制对于卖方也是先验独立的，这意味着我们的结果的实际意义。
英文摘要：
A prevalent market structure in the Internet economy consists of buyers and sellers connected by a platform (such as Amazon or eBay) that acts as an intermediary and keeps a share of the revenue of each transaction. While the optimal mechanism that maximizes the intermediary's profit in such a setting may be quite complicated, the mechanisms observed in reality are generally much simpler, e.g., applying an affine function to the price of the transaction as the intermediary's fee. Loertscher and Niedermayer [2007] initiated the study of such fee-setting mechanisms in two-sided markets, and we continue this investigation by addressing the question of when an affine fee schedule is approximately optimal for worst-case seller distribution. On one hand our work supplies non-trivial sufficient conditions on the buyer side (i.e. linearity of marginal revenue function, or MHR property of value and value minus cost distributions) under which an affine fee schedule can obtain a constant fraction of the intermediary's optimal profit for all seller distributions. On the other hand we complement our result by showing that proper affine fee-setting mechanisms (e.g. those used in eBay and Amazon selling plans) are unable to extract a constant fraction of optimal profit in the worst-case seller distribution. As subsidiary results we also show there exists a constant gap between maximum surplus and maximum revenue under the aforementioned conditions. Most of the mechanisms that we propose are also prior-independent with respect to the seller, which signifies the practical implications of our result.
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