This paper examines how strengthening patent protection affects welfare in a nonscale quality-ladder model, which was developed by Segerstrom [American Economic Review 88, 1290–1310] and generalized by Li [American Economic Review 93, 1009–1017]. In the Segerstrom–Li model, patent protection creates no distortion in static allocation among the production sectors. In order to examine the welfare effects of strengthening patent protection adequately, we incorporate a competitive outside good into the Segerstrom–Li model. In the general model, we derive the welfare-maximizing degree of patent protection analytically by utilizing a linear approximation of the transition path. The result shows that the welfare-maximizing degree of patent protection is weaker when the market share of the outside good is positive than when it is zero. In other words, disregarding the static distortion that patent protection creates leads to excessive patent protection.
