Apparently the evidence is mixed on the importance of patents as an incentive to innovation, though it always seemed intuitive to me that patents should matter. Petra Moser has just published research from his dissertation, that seems to add evidence on the side of patents mattering:
How Do Patent Laws Influence Innovation? Evidence from Nineteenth-Century World’s Fairs
Abstract: Studies of innovation have focused on the effects of patent laws on the number of innovations, but have ignored effects on the direction of technological change. This paper introduces a new dataset of close to fifteen thousand innovations at the Crystal Palace World’s Fair in 1851 and at the Centennial Exhibition in 1876 to examine the effects of patent laws on the direction of innovation. The paper tests the following argument: if innovative activity is motivated by expected profits, and if the effectiveness of patent protection varies across industries, then innovation in countries without patent laws should focus on industries where alternative mechanisms to protect intellectual property are effective. Analyses of exhibition data for 12 countries in 1851 and 10 countries in 1876 indicate that inventors in countries without patent laws focused on a small set of industries where patents were less important, while innovation in countries with patent laws appears to be much more diversified. These findings suggest that patents help to determine the direction of technical change and that the adoption of patent laws in countries without such laws may alter existing patterns of comparative advantage across countries. (JEL D2, K11, L51, N0, O14)
Moser, Petra. “How Do Patent Laws Influence Innovation? Evidence from Nineteenth-Century World Fairs.” The American Economic Review 95, no. 4 (2005): 1214-1236.