Science and engineering departments with doctoral students from several different countries tend to produce more publications and to win more citations, a US study has found.

Skilled Immigration and Innovation: Evidence from Enrolment Fluctuations in US Doctoral Programmes argues that when scholars are drawn from across the world, they bring complementary skills and ideas that aid research.

The paper¡¯s researchers analysed a database of US and foreign doctoral students at 2,300 science and engineering departments in the US from 1973 to 1998.

They looked at how many publications were produced each year and at the number of citations garnered by the papers.

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If a department had 10 foreign students from five different global regions, it would on average produce 0.76 more publications and win 28.65 more citations a year than one where the international students hailed from just two regions, the research found.

¡°Diversity may result in positive spillovers from the exchange and mixing of ideas and methods if students from different regions bring complementary and heterogeneous skills,¡± the paper says.

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However, it does caution that the statistical evidence for this effect is ¡°limited¡± and that problems with communication and coordination for students from across the world may offset some of the benefits of diversity.

The article was written by Eric Stuen, assistant professor of economics at the University of Idaho, Ahmed Mushfiq Mobarak, associate professor of economics at Yale University, and Keith Maskus, professor of economics at the University of Colorado at Boulder, and is published in the December edition of The Economic Journal.

It finds that international students on scholarships contributed more citations to their department than those who had to pay full fees because entry standards were higher for those who won scholarships.

This discovery has implications for visa policy, the paper says. Rather than issuing visas to students who have ¡°financial wealth sufficient to support graduate study and return home¡±, the authors argue that students should be allowed in to the US based on their quality by looking at, for example, whether they have won a scholarship to a top-ranked course.

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US and international students produce similar numbers of publications and citations, the research found.

This suggests that departments generally achieve the most efficient balance between the two groups, the authors suggest.

¡°Proponents of increasing the numbers of foreign graduate students seem to be correct, in that they clearly have had a positive effect on the conduct of science.¡± However, the US supplies ¡°an equally high-quality contingent¡±, the paper says.

Any policies, including restrictions on visas, that keep doctoral students of any nationality away from US science and engineering departments could have a ¡°potentially large¡± impact on the US economy because it depends on innovation and new markets for growth, the paper concludes.

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The findings come amid debate on both sides of the Atlantic over immigration policy for international students, the paper notes, and in both the US and the UK academics have voiced concern over the potential economic impact of greater restrictions on foreign students.

The UK government has pledged to reduce net migration to below 100,000 a year by 2015, although there is no direct cap on student visas.

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david.matthews@tsleducation.com.