Tianle Zhang

Entry and Welfare in Search Markets

The effects of entry on consumer and total welfare are studied in a model of consumer search. Potential entrants differ in quality, with high-quality sellers being more likely to meet consumer needs. Contrary to the standard view in economics that more entry benefits consumers, we find that consumer welfare has an inverted-U relationship with entry cost, and free entry is excessive for both consumer and total welfare when entry cost is relatively low. We explain why these results may arise naturally in search markets due to the variety and quality effects of entry, and discuss their business and policy implications.

Group Coupons: Interpersonal Bundling on the Internet

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 interpersonal bundling is a profitable strategy in the presence of demand uncertainty, and how it may further boost profits by stimulating product information dissemination. Other reasons for its profitability are also discussed. We provide sufficient conditions for interpersonal bundling to dominate separate selling, and identify factors that determine the size of its profit advantage.

PATENTABILITY, R&D DIRECTION, AND CUMULATIVE INNOVATION: PATENTABILITY AND R&D DIRECTION

We present a model of cumulative innovation where firms can conduct R&D in both a safe and a risky direction. Innovations in the risky direction produce quality improvements with higher expected sizes and variances. As patentability standards rise, an innovation in the risky direction is less likely to receive a patent that replaces the current technology, which decreases the static incentive for new entrants to conduct risky R&D, but increases their dynamic incentive because of the longer duration---and hence higher reward---for incumbency. These, together with a strategic substitution and a market structure effect, result in an inverted-U shape in the risky direction but a U shape in the safe direction for the relationship between R&D intensity and patentability standards. There exists a patentability standard that induces the efficient innovation direction, whereas R&D is biased towards (against) the risky direction under lower (higher) standards. The optimal patentability standard may distort the R&D direction to increase the industry innovation rate that is socially deficient.