Consumer Heterogeneity and Paid Search Effectiveness: A Large-Scale Field Experiment
通过在eBay开展的大规模实地实验，发现付费搜索广告的因果效果远低于非实验估计，品牌关键词广告无短期收益，非品牌关键词广告仅对新用户和低频用户有效，而高频用户不受影响却消耗大部分广告支出，导致平均回报为负。
Internet advertising has been the fastest growing advertising channel in recent years with paid search ads comprising the bulk of this revenue. We present results from a series of large-scale field experiments done at eBay that were designed to measure the causal effectiveness of paid search ads. Because search clicks and purchase intent are correlated, we show that returns from paid search are a fraction of non-experimental estimates. As an extreme case, we show that brand-keyword ads have no measurable short-term benefits. For non-brand keywords we find that new and infrequent users are positively influenced by ads but that more frequent users whose purchasing behavior is not influenced by ads account for most of the advertising expenses, resulting in average returns that are negative. ∗We are grateful to many eBay employees and executives who made this work possible. We thank Susan