When the patent on a drug expires, there are substantial welfare gains to those consumers who, like the Food and Drug Administration, regard branded and generic versions as perfect substitutes. Standard price indexes fail to reflect this, since they treat generics as distinct new goods and "link them in" with fixed weights. Alternative calculations are presented, using detailed data on the wholesale prices of two anti-infective drugs. Significant differences are found: for one of the drugs studied the standard price index rose by 14 percent over 45 months following patent expiration, while our preferred alternative index fell by 48 percent.

Analysis of the timing of launches of 642 new drugs in 76 countries during 1983–2002 shows that patent and price regulation regimes strongly affect how quickly new drugs become commercially available in different countries. Price regulation delays launch, while longer and more extensive patent rights accelerate it. Health policy institutions and economic and demographic factors that make markets more profitable also speed up diffusion. The estimated effects are generally robust to controlling for endogeneity of policy regimes with country fixed effects and instrumental variables. The results highlight the important role of policy choices in driving the diffusion of new innovations.