【摘要】 网上市场供给侧的质量不确定性严重制约了网上交易规模的进一步扩大。本文针对当前中国各大网上交易平台纷纷引入新型的平台主导型认证机制的现象，通过构建两个递进式的比较静态模型，分别梳理了平台主导型认证机制的引入和认证标准调整对市场供给侧的影响机理，并以淘宝网的金牌卖家认证为例，利用准实验匹配方法进行了实证检验。本文研究表明：平台主导型认证机制的引入通过逆向选择弱化效应和道德风险弱化效应两条途径改善了网上市场卖家的平均质量。在卖家个体层面，认证标准的提高一方面能够提高留在市场中的获得认证卖家和未获得认证卖家的平均质量，另一方面也增加了留在市场中的获得认证卖家和未获得认证卖家的商品销量。但市场中的认证标准并非越高越好，因为在卖家层面，认证标准提高时会使部分中等质量卖家失去认证标志甚至是被迫退出市场；在行业层面，认证标准的提高只会同时增加市场中未获得认证卖家的数量以及未获得认证卖家整体的商品销量，而对获得认证卖家数量和获得认证卖家总销量的影响并不确定，最终使市场的质量分布在非认证卖家一侧出现明显的“厚尾”。更多还原

【Abstract】 The quality uncertainty on the supply side of the online market has severely restricted the further expansion of the online transaction scale. Focusing on the current phenomenon that major online trading platforms in China have introduced new platform-led certification mechanisms, this paper constructs two progressive comparative static models to examine how the introduction of platform-led certification mechanisms and the adjustment of certification standards affect the supply side of the market. Taking the gold-medal-seller of Taobao as an example, this paper conducts an empirical test by using the quasi-experimental matching method. The research shows that the introduction of a platform-led certification mechanism has improved the average quality of sellers in the online market through two ways: adverse selection weakening effect and moral hazard weakening effect. At the individual seller level, the improvement of certification standards can not only improve the average quality of certified sellers and non-certified sellers remaining in the market, but also increase the sales volume of certified sellers and non-certified sellers remaining in the market. However, it is not always the case that raising certification standards in the market is better. The reason is that, at the seller level, when the certification standards is raised, some medium-quality sellers will lose their certification or even be forced to withdraw from the market; at the industry level, the increase in certification standards will only increase the number of non-certified sellers and the overall sales volume of non-certified sellers in the market at the same time, but the impact on the number of certified sellers and the total sales of certified sellers is uncertain, resulting in an obvious “thick tail” in the quality distribution of the market on the side of non-certified sellers.更多还原