Science thomsonreuters.com

Despite continuing erosion of the US share of world science, the citation impact of its scientific papers still surpasses the world average in major scientific fields.

Share in world science
Science Watch used the Thomson Reuters National Science Indicators database to examine global publication and citation statistics in science and the social sciences. Analysis of scientific output in all fields by over 170 countries shows a steady decline in the U.S. percent share from 1993 to 2007, compared to aggregate figures the Asia Pacific and European Union. Since the last comparison of this type in 2005, the Asia Pacific percentage has increased from 25.9 per cent to 28.2 per cent, while the U.S. share has slipped from 32.8 per cent to 31.5 per cent in 2007. Research share by the European Union is also trending downward, dropping from 38.0 per cent to 37.3 per cent in 2007.

Increasing scientific output by the nations of Asia, combined with increasing international collaboration and co-authorship on scholarly papers, accounts significantly for the Asia Pacific group exhibiting a greater presence in world science. But it should be noted the absolute number of Thomson Reuters-indexed scientific papers from the U.S. has edged downward: from a high of roughly 291,500 in 2005 to approximately 286,000 in both 2006 and 2007.

Citation impact
Measured by citation impact, U.S. science still appears quite healthy. Science Watch examined U.S. world share and citation impact in 21 main fields of science, ranked according to those fields in which U.S. "relative impact" is well above the world average over a recent five-year period. Physics tops the list with a U.S. impact mark of 6.15 cites per paper—surpassing the world mark of 3.96 cites by 55 per cent.

Research fronts
For another snapshot of current U.S. science, Science Watch turned to the Thomson Reuters unique store of Research Fronts—emerging areas of research that are identified by a foundational "core" of papers that are frequently cited together. A sampling of eight Research Fronts shows U.S.-based institutions listed among the collective author addresses for each grouping of core papers. Thus, the list constitutes a small selection of U.S. concentration in recent research, featuring subjects including:

• genome-wide mapping of chromatin state in the cell
• processes for creating zirconium diboride and silicon carbide ceramics
• phase 0 trials in cancer therapy

See the full Science Watch analysis

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