Patent–Paper Citation Linkage (NPL)

Patent–paper citation linkage measures how strongly technology draws on science by analyzing the non-patent literature, or NPL, references that appear on patents. When a patent cites a scientific journal article rather than another patent, it leaves a traceable thread connecting an invention to the research it built on. Francis Narin, Kimberly Hamilton, and Dominic Olivastro's landmark 1997 study traced these threads at national scale and found that the citation linkage between U.S. patents and scientific papers was growing rapidly, that the cited science was overwhelmingly public, authored in universities and government laboratories, and that this linkage offered a quantitative measure of the contribution of public science to industrial technology. The resulting science-linkage indicator distinguishes science-intensive technologies from incremental ones and underpins studies of how publicly funded research feeds private innovation.