中文摘要：

针对付费搜索对搜索引擎结果排名的影响，建立以“顺序浏览”为特征的用户搜索模型，通过将模型预测结果与实际数据分布的比较对模型进行检验，进一步定义以信息代价为衡量标准的排名质量定量测度方法，并设计一个数值实验评价两种不同排名机制下付费搜索对排名质量的影响，指出付费排名相对自然排名给用户所增加的搜索代价比与SERP结果质量差异成正相关关系，但在有效竞价排名下该比例会有所减小。

英文摘要：

Aiming at the effects of sponsored search on the quality of the ranking of SERP results, this article builds a search user behavioral model with the characteristics of ordinal browsing. After checking the model by comparison between the theoretic and practical results, it defines a measure of ranking quality based on information transition cost and assesses the ranking quality of sponsored search under two dif- ferent mechanisms by designing a numerical experiment. It concludes that the ratio of user＇ s extra search cost of the sponsored ranking to natural ranking increases with the quality variances of SERP results, but the ratio will be smaller in the ranking by effective bids.