R&D Portfolio and Market Structure
分析企业在多个异质性研究项目中竞争专利时如何分配资源，发现即使无模仿且企业完全理性，资源分配仍偏向规避风险和基础研究，导致市场可能缺乏重大创新；同时市场越竞争，企业基础研究投入越少、风险研究越多，为创新与市场集中度的模糊关系提供新解释。
This article analyses how firms allocate their resources when they compete for multiple patents in heterogeneous research projects simultaneously. A simple model shows that firms' resource allocation is biased away from risky and basic research, even when imitation is not possible and firms are fully rational. Therefore a market may lack major innovations despite large aggregate research expenditure and strong patent protection. This article also shows that as a market becomes more competitive, firms invest relatively less in basic research but more in risky research. These results provide a novel explanation for an ambiguous empirical relationship between innovation and market concentration. Copyright © The Author(s). Journal compilation © Royal Economic Society 2009.