Innovation Variety and Patent Breadth
当创新具有异质性时，提供多样化的专利可能更优。通过权衡专利宽度与长度，最优政策可能无需费用。本文用质量阶梯模型和水平产品差异化两个例子说明，更富创造力的创新获得更短时间但更宽的专利保护。
When innovations are heterogeneous, it may be advantageous to provide a variety of patents. By trading off patent breadth for length, it is possible that fees are not needed in the optimal policy. We present two examples. The first is a quality-ladder model, in which innovations benefit society directly as well as through their use as building blocks to future inventions, and the rate of arrival for the future innovation is unobserved. More fertile innovations get more breadth for a shorter time. Menus may also be useful in the case of horizontal product differentiation.