Clear and well-defined patent rights can incentivize innovation by granting monopoly rights to the inventor for a limited period of time in exchange for public disclosure of the invention. However, with cumulative innovation, when a product draws from intellectual property held across multiple firms (including fragmented intellectual property or patent thickets), contracting failures may lead to suboptimal economic outcomes. However, an alternative theory, developed by a variety of scholars, contends that patent thickets have a more ambiguous effect. Researchers have developed several measures to gauge the extent and impact of cumulative innovation and the various channels of patent thickets. This paper contends that mis-measurement may contribute to the incoherence and overall lack of consensus within the patent thickets literature. Specifically, the literature is missing a precise measure of vertically overlapping claims. We propose a new measure of vertically overlapping claims that incorporates invention similarity to more precisely identify inventive overlap. The measure defined in this paper will enable more accurate measurement, and allow for novel economic research on cumulative innovation, fragmentation in intellectual property, and patent thickets within and across all patent jurisdictions.
