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National Science Foundation National Center for Science and Engineering Statistics
Changing U.S. Output of Scientific Articles: 1988-2003



Purpose and Scope

Scientists and engineers ordinarily publish their research results in peer-reviewed journal articles. The number of these articles is an indicator of research output, although an admittedly imperfect one. Citations to these articles are an indicator, also imperfect, of the extent of the cited article's influence. In recent years, international use of these and related indicators has become widespread as countries have sought to assess their relative performance in S&E research.

This report is part of a larger study by the National Science Foundation (NSF), Division of Science Resources Statistics (SRS), on changing patterns and trends in U.S. production of scientific articles since the late 1980s. The study was initiated in light of evidence that the growth in the number of U.S. articles, which had continued for more than two decades, began to slow in the 1990s even though R&D funds, research personnel, and similar research inputs continued to grow.

SRS plans to publish results from this study in a series of three reports, each focused on a different aspect of the issue. The present report is purely descriptive and does not attempt to speculate about explanations for the findings. It presents quantitative data on patterns and trends in article production and citations during the 15-year period between 1988 and 2003. The second report, The Changing Research and Publication Environment in American Research Universities (http://www.nsf.gov/statistics/srs07204), which is based on qualitative data from interviews and focus groups, summarizes the views of experienced observers and practitioners in research universities about how the worlds of academic S&E research and publication changed during the study period. Some of the observations in that report bear on possible explanations of the patterns and trends in the quantitative data reported here. A third report (forthcoming) analyzes quantitative data on research inputs and outputs in the U.S. academic sector to explore possible factors associated with the patterns and trends described in the first two reports. None of the reports speculate about possible policy implications of the findings.

This report is confined to a presentation of data derived from the most comprehensive database available on scientific publications. It makes no attempt to cover the large, dispersed literature bearing on various aspects of the changing environment for research and publication (e.g., Stephan et al. on faculty commercialization and publication activities; Stossel and Stossel on publication patterns in a single discipline; Cummings and Kiesler on multidisciplinary and multiinstitutional research; Tijssen on changes in publication practices in the industrial sector; Tenopir and King on the rise of electronic journals).[1] Nonetheless, these more targeted studies and others like them, which use other, more theoretically driven analytic models and less-comprehensive databases, suggest significant avenues for further research. In many cases, studies such as these prompted examination of the patterns presented in this report.

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Organization of the Report

This report is divided into a methodological section and three substantive sections. The methodological section discusses the database, selection of the journal set, and various ways to count articles. The first substantive section examines and compares overall trends in S&E article production in four major publishing centers: the United States, the EU-15, Japan, and the East Asia-4.[2] This section also includes a description and comparison of trends in national article outputs in the different S&E fields. Subsequent sections examine patterns and trends in strategically important parts of the research enterprise. The second substantive section focuses on influential (i.e., highly cited) articles and journals. These articles and journals are important because a nation's involvement in influential research indicates worldwide leadership in S&E and can have implications for economic and technological leadership. The third substantive section describes trends in the output of the U.S. academic sector. This sector produces the most articles of any U.S. sector. Developments in this sector therefore are especially important to the overall health of a nation's research system and affect the nation's ability to attract and retain talented researchers from other countries. This section pays particular attention to the top U.S. research universities.[3] Research is central to the overall mission of these institutions, many of which achieve or aspire to worldwide recognition as research leaders. These institutions thus comprise the most strategically important part of this institutional sector.

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The number of science and engineering (S&E) articles published by U.S.-based authors in the world's major peer-reviewed journals leveled off in the 1990s. Publications had risen over at least the two preceding decades, and a plateau was unexpected given that resource inputs that support R&D, such as funds and personnel, continued to increase.

This unprecedented, prolonged plateau in absolute number of U.S. S&E articles, accompanied by steady rises in resource inputs, provided the impetus for this study and gave it its central focus. It should not be confused with a decades-long and familiar decline in the U.S. share of the world's S&E articles, see figure Figure..

The U.S. share of the world's articles in natural sciences and engineering dropped from 38% in 1973 to 28% in 2003. This decline in share, reflecting the build-up of other nations' S&T systems, is not surprising and has not been viewed as a cause for concern. By many measures, including articles published in peer-reviewed journals, the United States has been the world's leading scientific nation for decades and remains the world's leading scientific nation.

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[1] Stephan, P.E., S. Gurmu, A.J. Sumell, and G. Black. Who's Patenting in the University? Evidence from the Survey of Doctorate Recipients. Forthcoming in Economics of Innovation and New Technology. http://www2.gsu.edu/~ecosgg/research/pdf/sgsb_eint.pdf. Accessed December 2006.; Stossel, T.P. and S.C. Stossel. 1990. Declining American Representation in Leading Clinical Research Journals. New England Journal of Medicine 322 (11): 739-42.; Cummings, J.N. and S. Kiesler. 2005. Collaborative Research Across Disciplinary and Organizational Boundaries. Social Studies of Science 35/5 (October): 703-722.; Tijssen, R.J.W. 2004. Is the commercialisation of scientific research affecting the production of public knowledge? Global trends in the output of corporate research articles. Research Policy 33: 709-33.; Tenopir, C. and D.W. King. 2000. Towards Electronic Journals: Realities for Scientists, Librarians, and Publishers. Washington, D.C.: SLA Publishing.

[2] The four major publishing centers accounted for 78% of world S&E article production in 2003.

[3] Based on total R&D expenditures during the 1988–2001 period.

Changing U.S. Output of Scientific Articles: 1988-2003
Special Report | NSF 07-320 | July 2007