Paid placement, where advertisers bid payments to a search engine to have their products appear next to keyword search results, has emerged as a predominant form of advertising on the Internet. This paper studies a product-di¤erentiation model where consumers are initially uncertain about the...

Sellers sometimes offer goods for sale under both a regular price and a discount for group purchase if the consumer group reaches some minimum size. This selling practice, which we term interpersonal bundling, has been popularized on the Internet by companies such as Groupon. We explain why...

An important issue in economics is how market structure affects prices. While the standard view is that competition lowers prices, Chen and Riordan (2006) argued that with product differentiation it is not exceptional for prices to be higher under duopoly than monopoly. This paper empirically...