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Post-grant validity challenges at patent offices rely on the private initiative of third parties to correct mistakes made by patent offices. We hypothesize that incentives to bring post-grant validity challenges are reduced when many firms benefit from revocation of a patent and when firms are caught up in patent thickets. Using data on opposition against patents at the European Patent Office we show that opposition decreases in fields in which many others profit from patent revocations. Moreover, in fields with a large number of mutually blocking patents the incidence of opposition is sharply reduced, particularly among large firms and firms that are caught up directly in patent thickets. These findings indicate that post-grant patent review may not constitute an effective correction device for erroneous patent grants in technologies affected by either patent thickets or highly dispersed patent ownership.

With permission of the Academy of Management

The ‘variance hypothesis’ predicts that external search breadth will lead to innovation outcomes, but time for search is fixed and cultivating breadth takes time. How does individuals’ external search breadth affect innovation outcomes? We match survey data with complete patent records, to examine the search behaviors of elite experts at one of the world’s most innovative firms. Counter to expectations, individuals who spent more time inside the firm were more likely to be innovative. Individuals with high external search breadth were more innovative only when they allocated more attention to those sources. Our research identifies limits to the ‘variance hypothesis’ and reveals two successful approaches to innovation search: ‘cosmopolitans’ who cultivate and attend to external sources and ‘locals’ who draw upon internal sources.

With permission of the Academy of Management