Network Effects and Diffusion in Pharmaceutical Markets: Antiulcer Drugs

We examine the role of network effects in the demand for pharmaceuticals at both the brand level and for a therapeutic class of drugs. These effects emerge when use of a drug by others conveys information about its efficacy and safety to patients and physicians. This can lead to herd behavior where a particular drug -- not necessarily the most efficacious or safest -- can come to dominate the market despite the availability of close substitutes, and can also affect the rate of market diffusion. Using data for H2-antagonist antiulcer drugs, we examine two aspects of these effects. First, we use hedonic price procedures to estimate how the aggregate usage of a drug affects brand valuation. Second, we estimate discrete-time diffusion models at both the industry and brand levels to measure the impact on rates of diffusion and market saturation.