Patentability, R&D Direction, and Cumulative Innovation

We present a model where firms conduct R&D in both a safe and a risky direction. As patentability standards rise, an innovation in the risky direction is less likely to receive a patent, which decreases the static incentive for new entrants to conduct risky R&D but can increase their dynamic incentive. 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. R&D is biased toward (against) the risky direction under lower (higher) standards.