Thematic coherence of innovation systems: a patent-based index

We propose a novel measure of thematic coherence of national innovation systems, based on the comparison of distributions of patent applications submitted by business and academia. The index is calculated for a number of countries using data on more than 5 million priority filings from 1990 to 2016. Cluster analysis suggests a complex relationship of thematic coherence with other aspects of national innovation systems, with two quite different groups of countries showing high level of the index. The estimates of knowledge production function indicate that more coherent systems obtain more innovation outputs per unit of research input.