Search Advertising
研究了搜索引擎如何根据用户查询定向投放广告，发现定向能降低搜索成本、改善匹配并加剧价格竞争，但垄断搜索引擎的高广告费可能抵消这些好处，且竞争搜索引擎的福利效果取决于广告商的多归属程度。
Search engines enable advertisers to target consumers based on the query they have entered. In a framework in which consumers search sequentially after having entered a query, I show that such targeting reduces search costs, improves matches and intensifies price competition. However, a profit-maximizing monopolistic search engine imposes a distortion by charging too high an advertising fee, which may negate the benefits of targeting. The search engine also has incentives to provide a suboptimal quality of sponsored links. Competition among search engines can increase or decrease welfare, depending on the extent of multi-homing by advertisers.