When the quadrennial International Congress of Mathematicians took place at the University of California, Berkeley in 1986, almost half of the 80 speakers came from the Soviet Union.

Almost a quarter of a century later, just five of the 170 speakers invited to address the 2010 congress in Hyderabad, India, were affiliated with Russian universities.

The exodus of ¸é³Ü²õ²õ¾±²¹¡¯²õ best mathematicians to the West since the disintegration of the Soviet Union is often illustrated with such potent anecdotes, but two Moscow-based academics have now sought to quantify what the traditional maths powerhouse has lost during the early-1990s brain drain and what the emigrants¡¯ host countries have gained.

Vladlen Timorin, professor and dean of mathematics at the Higher School of Economics at the National Research University in Moscow, and Ivan Sterligov, head of the institution's scientometric centre, decided to analyse all the international journal papers published in maths by people with surnames most commonly found in Russia.

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The pair found that in 1994 around 70 per cent of these Russian-surnamed publications came from Russian institutions, but by 1997 this tally fell to approximately 50 per cent, and has remained roughly at this level.

Just over a third of maths papers published by those with a Russian surname were based in the US between 1993 and 2015 ¨C of which most are likely to be Russian emigrants, the duo suggest.

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A further 10 per cent of maths papers authored by those with Russian surnames over the same period came from France (also well known for its outstanding mathematicians), while 8 per cent were in Germany, 8 per cent in the UK and 7 per cent in Canada, , ¡°A metric view on Russian mathematics and Russian mathematical diaspora¡±, published in the journal Higher Education in Russia and Beyond.

Russian mathematicians operating outside their home country also appear to enjoy better reputations than those in their homeland, the authors add.

Of those mathematicians with Russian names who were published in a ¡°top 25 journal¡±, 203 were based outside Russia, compared with just 83 working inside their homeland ¨C while the former cohort¡¯s citation rate is three times as high as that inside Russia.

¡°We can conclude that the overseas part of [¸é³Ü²õ²õ¾±²¹¡¯²õ mathematicians] are more efficient in their research, at least in terms of metric values,¡± the authors say.

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¡°Russian emigrants appearing in our data sheets are¡­able to find good academic positions abroad and¡­appear to be more productive than domestic scientists in their host countries,¡± they add.

With an estimated 1,000 mathematicians alone leaving Russia for the US in the early 1990s and all but one of its Fields Medal winners (seven since 1990) based abroad, the researchers conclude that ¡°Russian mathematics has lost its best representatives¡±.

However, there is some cause for optimism. The brain drain appears to have slowed, with those in Russia performing well on international citation indexes.

¡°Russian mathematical output stands surprisingly high despite the exodus of a better part of mathematicians,¡± they conclude.

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?jack.grove@tesglobal.com