Scientists that more frequently change the city where they are based are more likely to be highly cited, a new data analysis suggests.

In 15 out of 20 cities whose research output was analysed, transitory researchers ¨C defined as those who stayed for less than two years ¨C had the highest average citation impact.

The finding comes in?, co-produced by Elsevier and a public body overseeing Shanghai¡¯s research and development integration, comparing the data on research in different cities.

Using an analysis of author affiliations on publications in Elsevier¡¯s Scopus database of indexed research from 1996 to 2017, the report finds that Paris, and the Chinese cities of Shanghai and Shenzhen, had the highest ¡°inflow¡± of researchers.

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In contrast, Beijing, Boston and Berlin had the highest ¡°outflow¡± of researchers, measured as the share of their authors who left the city and then did not return.

It suggests this could ¡°reflect the resources concentration advantages of these cities in cultivating young and active researchers¡± but may also show that the locations do not have enough incentives to entice scientists to stay long term.

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Other cities had a high share of researchers classed as ¡°sedentary¡± because their affiliations indicated they had not published outside the location. This was led by Seoul (31.3 per cent of researchers), Moscow (29.7 per cent) and Shanghai (25 per cent).

The report says that a high proportion of inflowing and sedentary researchers could be ¡°important factors in ensuring the stable development of a city¡¯s scientific research¡± but also points out that the sedentary group tended to be cited the least.

In contrast, out of the cities considered in the report, transitory researchers most often had the highest field-weighted citation impact (FWCI), a measure that takes the year and discipline of publications into account.

For some locations, the difference in citation impact between transitory and sedentary researchers was quite large: those spending a short amount of time in Moscow, for instance, had a FWCI of more than twice the world average compared with about half the world average for those never leaving the city.

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There were five main exceptions to the trend of transitory researchers being more highly cited ¨C Boston, London, New York, San Francisco and Singapore ¨C where scientists flowing into the locations, and then staying there, tended to have the highest FWCI.

Overall ¨C when analysing more recent publications from 2014 to 2018 ¨C San Francisco, Boston, Amsterdam and Los Angeles were the top four cities for citation impact with a FWCI value more than twice that of the world average.

Hong Kong, Stockholm and Singapore were meanwhile the top cities for the highest share of internationally collaborative publications with almost two-thirds of research in each location featuring cross-border working.

And San Francisco, New York and Osaka were the top three cities with the largest share of publications written collaboratively between academia and industry.

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simon.baker@timeshighereducation.com