Using a new global data base on patents and innovation inputs, the authors examine the process of knowledge creation measured by the dynamic relationship between research and development and U.S. patents granted. They confirm at the country level the recurrent micro-level finding of a strong relationship between the two and estimate the OECD elasticity to be effectively equal to one. This conflicts with the frequent micro-level finding of strongly diminishing returns in knowledge generation and suggests the importance of knowledge spillover effects measurable only at the aggregate level. Developing countries, however, do show diminishing returns. The authors then explain the differences in spillovers between the OECD and developing countries by testing for the impact of measures of the functioning of the national innovation system-the set of institutions and agents that create and disseminate knowledge. Across the entire sample education, security of intellectual property rights, and in some specifications, the quality of research institutions and their interaction with the private sector, affect the transformation of research and development into patents.