But when they do work with colleagues outside the continent, European researchers get a proportionally greater citation boost than US researchers, according to by Science Europe and the publisher Elsevier.

Studies have previously shown that collaborative research typically results in higher citations - a measure of the impact of research articles - with ¡°outside region¡± collaboration having the greatest citation benefit.

Both Europe and the US have experienced steady growth in their overall collaboration rates since 2003, shows the study, which used data from the Scopus database to compare patterns in research collaboration between the US and Europe.

It found that, at 13 per cent of research articles, inter-country collaboration in Europe is still below that of inter-state collaboration in the US, where it accounts for 16 per cent of papers.

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However the difference is diminishing, with inter-country collaboration in Europe increasing, having risen to 13 per cent of articles from slightly over 11 per cent in 2003. Meanwhile the US figure has fallen, adds the report.?

Comparative Benchmarking of European and US Research Collaboration and Researcher Mobility, published on 12 September, also found that US researchers were more likely to collaborate with people outside their own region than European researchers. It found 30 per cent of articles were co-authored with academics affiliated to institutions outside the US, compared with an equivalent figure of 23 per cent for Europe.

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While the pool of available collaboration partners outside of Europe is smaller than that available outside the US, because there are more researchers in Europe than the US, the difference is fairly small and would not be enough to explain these percentage differences, the report adds.

It also looked at migration patterns of researchers in the two regions by looking at their affiliations over a 15-year period.?

Despite similar collaboration patterns between countries in Europe as between states in the US, it found that migration of researchersbetween different countries within Europe was considerably less frequent than between states in the US.

¡°One might argue that the attitude among funding agencies to allowing the grants they have awarded to move across borders may be part of the explanation for this,¡± reads the report.?

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¡°However, factors that are more likely to be influential would include the differences in culture, language, administrative systems, benefits, pensions and other support systems, which continue to vary considerably across Europe.

¡°In the US, there is greater comparability of employment law and compensation packages between states,¡± it adds.

Paul Boyle, president of Science Europe, said the findings would help understand the current status of collaboration and mobility of the research communities and serve as a basis to drive effective policy.

¡°The report provides new benchmarks which will be invaluable to reference in the future to assess the impact of research policies within the European Research Area,¡± he added.

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Encouraging cross-country collaboration, mobility of grants and researchers and alignment of career structures is an aim of the European Commission, which is seeking to create the European Research Area, a single market for research, by 2014.

elizabeth.gibney@tsleducation.com