An analysis of the evolution of science-technology linkage in biomedicine

Highlights

• Patent-to-paper citations in a 37-year period are analyzed.

• There is an exponential growth of patent-to-paper citations, doubling every 2.9 years.

• Different dimensions of cited science are studied.

• For the majority of companies, more than half of citations in their patents are authored by public research.

Abstract

Demonstrating the practical value of public research has been an important subject in science policy. Here we present a detailed study on the evolution of the citation linkage between life science related patents and biomedical research over a 37-year period. Our analysis relies on a newly-created dataset that systematically links millions of non-patent references to biomedical papers. We find a large disparity in the volume of citations to science among technology sectors, with biotechnology and drug patents dominating it. The linkage has been growing exponentially over a long period of time, doubling every 2.9 years. The U.S. has been the largest producer of cited science for years, receiving nearly half of the citations. More than half of citations goes to universities. We use a new paper-level indicator to quantify to what extent a paper is basic research or clinical medicine. We find that the cited papers are likely to be basic research, yet a significant portion of papers cited in patents that are related to FDA-approved drugs are clinical research. The U.S. National Institute of Health continues to be an important funder of cited science. For the majority of companies, more than half of citations in their patents are authored by public research. Taken together, these results indicate a continuous linkage of public science to private sector inventions.

Introduction

There is a longstanding policy interest in unraveling how knowledge generated from public research is used in the private-sector. Studies towards this goal have heavily focused on patent data and considered citations between patents as evidence of knowledge flow. Despite some criticism (Meyer, 2000), such notion has been widely accepted in the literature. Consequently, substantial attention has been paid to patents assigned to universities and other public organizations, examining how those patents are cited by other patents, especially by patents from companies (Rosell & Agrawal, 2009; Trajtenberg, Henderson, & Jaffe, 1997).

University patents, however, only account for a small portion of granted patents, and the main products of public research are scholarly papers rather than patents. Just as patents, papers can also be cited by patents, and indeed both the cited patents and cited papers are served as the “prior art” of a patent application, playing a significant role for patent examiner to determine the patentability of the application. There has been a large literature on both the patent-to-patent and the patent-to-paper citation linkage. Yet, systematic studies, as we shall present in this paper, have been relatively scarce.

Our primary interest in this work is in the life science sector. The last several decades have seen an unprecedented rapid progress of life science, both in basic scientific discoveries and clinical medicine. Recent studies have suggested that biotechnology and pharmaceutical patents have been the main driver for the overall growth of patents and exhibit a particularly prominent citation linkage to science (Mowery, Nelson, Sampat, & Ziedonis, 2004). This has prompted us to ask: How has the patent-to-paper citation linkage of life science patents changed over time? In particular, we aim to answer the following lines of research questions:

• How has the amount of citations to science changed over time? Does the change vary across different technology classes?

• On the cited side of the linkage, which countries and types of institutions produce the cited papers? Whether basic or applied research are more likely to be cited?

• On the citing side, to what extent company patents cite public science?

These questions are important due to their high relevance to the policy community. Although the study of citations to science of patents has a long history, initiated by Narin and his colleagues in the 1980s (McMillan, Narin, & Deeds, 2000; Narin, Hamilton, & Olivastro, 1997; Narin & Olivastro, 1992), an up-to-date “status report” has been lacking in the literature, partially due to the daunting task of resolving non-patent references to corresponding scholarly papers. Even in Narin's landmark study (Narin et al., 1997), the analyzed patents were granted in two two-year periods (1987–1988 and 1993–1994). By contrast, our analysis covers patents from 1976 to 2012. Such a large-scale corpus allows us to probe how the citations to science have changed over time. By using a large sample over a 36-year period, we contribute to the literature a systematic accounting of linkage from technology to science. On the methodology side, we use a novel, paper-level indicator to quantify to what extent a paper is basic science or clinical medicine, allowing us to distill new insights on the science-technology linkage in biomedicine.

The rest of the paper is organized as follows. Section 2 discusses the context of our work. In Section 3, we describe the data source, selection of the cohort of patents analyzed in this work, and methods used to identify various properties of patents and cited papers. Section 4 presents the results of our analysis. Finally, we discuss and conclude in Section 5.