With Brexit negotiations under way and Donald Trump issuing his third travel ban in a year, discussion around freedom of movement is intensifying across higher education.

Researchers across the globe have long argued in favour of the right to remain mobile, and two new analyses ¨C using separate methodologies ¨C of the impact of global mobility on scientific influence could strengthen their case.

The two reports, both published in the journal Nature, suggest that policies that welcome immigrant scientists can significantly benefit both the scientific impact of individual researchers and the country they work in.

In , Cassidy Sugimoto, associate professor of informatics at Indiana University, led a team that analysed 14 million articles from nearly 16 million unique individuals publishing between 2008 and 2015. She and her colleagues found that scholars who moved during that time ¨C wherever they were working and wherever they were from ¨C had citation rates that were about 40 per cent?higher?on average than those who stayed put.

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The research also challenges the notion that academic mobility is a matter of ¡°brain gain¡± and ¡°brain drain¡±, finding that most internationally mobile researchers did not cut ties with their country of origin but ¡°instead built a chain of affiliations that linked nations together¡±, with many returning to their home country at some point.

Overall, 27.3 per cent of the mobile researchers in the sample began publishing in one country and then moved to another. But 72.7 per cent retained a footing in their country of scientific origin throughout their career, while also acquiring international affiliations.

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Among the researchers who moved from one continent to another, there was a significant net loss for Europe and Asia ¨C of 22 per cent and 20 per cent, respectively ¨C and a 50 per cent gain for North America.

¡°Internationally mobile scholars are in the minority, yet show the highest impact across the globe. Limiting the circulation of scholars will damage the entire scientific system,¡± the report concludes.

A detailing research undertaken by Caroline Wagner, chair of international affairs at Ohio State University, and Koen Jonkers, from the European Commission¡¯s Joint Research Centre, shows a strong relationship between a nation¡¯s scientific influence and the links that it fosters with foreign researchers.

According to the report¡¯s findings, this correlation is held regardless of a country¡¯s spending on research and development or the number of articles it publishes.

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The authors analysed science expenditure and article and citation data for 2.5 million scholarly publications from 2013 across 36 countries. They also combined metrics of international co-authorship and the mobility of the research workforce, suggesting that the reason for the correlation is that open countries are producing highly creative and innovative science.

Dr Wagner and Dr Jonkers found that some small nations, such as Switzerland and Singapore, punch above their weight (in terms of population size and science spending), whereas others ¨C notably South Korea ¨C are making less of an impact despite their high spending on R&D. The authors suggest that countries hoping to boost scientific impact should favour international exchange when awarding research and travel grants.

¡°Restricting the movement of researchers ¨C by limiting exchange opportunities or imposing visa restrictions, for example ¨C could be counterproductive,¡± they argue. ¡°Just as industries make ¡®build or buy¡¯ decisions, so governments must make ¡®link or sink¡¯ decisions about research investment.

¡°Our data add to a growing body of work about the changing science system, indicating that science policymakers who seek to enhance impact should prioritise international exchange.¡±

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rachael.pells@timeshighereducation.com