ver the last two decades, the European Union and Asia Pacific nations have steadily increased their world share of the journal literature in the physical sciences. In fact, these regions now surpass the United States in output of papers in physics, chemistry, and materials science, according to a new Science Watch survey, based on the  National Science Indicators database 1981-98, from the Institute for Scientific Information^® (ISI^®).

The chart below offers a specific illustration of this trend, showing world shares of papers in the field of physics over the last 18 years. On page 2, a table compares the percent shares of the European Union (EU) and the Asia Pacific nations (AP) against the U.S. share in 17 fields, at five- or six-year intervals since 1981. In 1997, Science Watch first reported on an apparent slide in the U.S. output of world science as reflected in share of published papers, with a concomitant rise in paper production by EU and AP nations (see Science Watch, 8[3]:1-2, May/June 1997). The present survey takes a closer look at this trend with a field-by-field analysis.

The field of physics (encompassing general physics, condensed-matter physics, high-energy physics, and optics and acoustics) offers a particularly striking example of the rise in output by EU and AP nations and the simultaneous U.S. decline. From its lead position in 1981, the U.S. share of physics papers began its slide in the early 1990s, as the EU's share continued upward. By 1996, the steadily upward-trending AP nations had surpassed the falling U.S. in world share. By 1998, the EU nations accounted for roughly 37% of published physics papers, compared to the AP's 29%, whereas the U.S. share hit a low of approximately 26%.

As science becomes ever more global—as developing nations begin to take their place alongside developed nations—one might expect that world-share statistics might start to converge. After all, world share is a zero-sum notion: if one gains share, another must lose. But the U.S. decline in world share in physics is accompanied by a decline in actual number of papers as well. Having reached a peak of 22,971 papers in physics in 1994, the number has declined slightly to 22,159 in 1998. Meanwhile, in 1998, the EU and AP nations reached all-time highs in output of physics papers: 32,178 and 24,941 respectively.

It should be emphasized that these output figures do not consider the citation impact of published papers. According to the measure of impact (that is, citations per paper), the comparative influence of U.S. papers in physics and other fields—regardless of any decline in world share—remains robustly healthy. In 1998, for example, U.S. physics papers were cited, on average, at a level 51% above the world average in the field, while EU physics papers exceeded the world average by 20% and AP physics papers scored an impact 24% below the world mark. The numbers are similar in chemistry, where the impact of U.S. papers surpassed the world figure by 53%, compared to an impact mark 10% above the world average for the EU and 25% below for the AP.