数量上限、付费位置拍卖与搜索引擎的排序行为

Upper Limit of Quantity,Sponsored Search Auction and Ranking Behavior of Search Engines

按照行业规制,中文搜索引擎企业对其付费搜索结果列表实施了位置数量上限的约束。这一约束在付费位置不定数的第二价格拍卖规则下,将对搜索引擎的排序行为产生影响。本文基于中国搜索引擎企业实践,以商品关键词检索领域的消费者层面数据为样本,构造契合消费者顺序检索习惯的实证框架,运用多层贝叶斯回归、断尾回归等分析工具,在数量上限的情形下,考察搜索引擎排序行为的匹配效应与利润效应,探究两者变化趋势是否一致及内在原因,进而对经典文献进行证实或证伪。研究发现:付费位置数量有上限时,搜索引擎排序行为的匹配效应随付费位置降低而凸型下降,且仅有最后1个付费位置的匹配效应为负值;搜索引擎排序行为的利润效应随付费位置降低而凹型下降,但仅有第1个付费位置的利润效应为正值,其他付费位置的利润效应皆为负值;两者呈现不一致性的主要原因是搜索引擎所设的拍卖底价并非理论上的最优拍卖底价,降低了搜索引擎汲取利润的能力。本文实证研究结论否定了经典文献所给出的两者一致性观点,有助于纵深推进付费位置拍卖的理论研究。

The sponsored search auction is the main source of search engine revenue and advertisers'bidding benefits.Due to the requirements of the government's industry regulation departments,search engines impose restrictions on the upper limit of the quantity of the sponsored positions,making it different from the common design of the sponsored positions with variable number.Little attention has been paid to the influence mechanism of auction design with limited quantity of sponsored positions on search engines and advertisers.By combing with the practice of Chinese search engines and using multi-layer Bayesian regression and other regression analysis,this paper constructs an empirical framework suitable for consumer retrieval behavior to investigate the influence mechanism of the sponsored auction with limited quantity of positions and explore the actual effect of industry regulation with that limit.The study found that the auction design with limited positions is equivalent to truncating the list of paid search results,which makes it easier for consumers to slide out of the paid search results area and makes it more difficult for search engines to obtain the click rate from consumers.To reduce the risk,on the basis of meeting the bidding rank rules,search engines need to give priority to the ranking rules considering the preferences of consumers to maximize the click rate from consumers on paid search results and increase the auction revenue of sponsored positions.However,under the best bidding rank rules,the contribution of advertisers to search engine excess profits is heterogeneous,meaning a small number of advertisers have a positive contribution to search engine excess profits,while most advertisers contribute negatively.It means that the limit of sponsored positions contributes to consumer welfare rather than search engine revenue.In essence,the limited quantity of positions provides a better constraint for search engines to improve information matching efficiency.