The practice of sponsored search advertising - where advertisers pay a fee to appear alongside particularWeb search results - is now one of the largest and fastest growing source of revenue for Web search engines. We model and compare several mechanisms for allocating sponsored slots, including...

Firms have traditionally used price and advertising to signal product quality when consumers are not initially well-informed about qualities of competing sellers. While the Internet has increased the frequency at which buyers face unknown sellers, it also provides abundant information about...