As you read this, the inaugural Times Higher Education Africa Universities Summit is under way at the University of Johannesburg.

It promises to be an illuminating event, with university leaders, politicians (including former South African president Thabo Mbeki) and academic and industry experts debating a wide range of issues.

One of these is how to tackle Africa¡¯s brain drain. At first glance, the factors behind this outflow of talent seem clear ¨C lack of infrastructure, funding and critical mass to name three. But the picture is much more nuanced when you get into the detail.

A 2014 report by the World Bank and Elsevier provides more insight into some of the issues at play.

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According to the report, an overwhelming majority of 85.3 per cent of southern African researchers have published a journal article while outside the region.

This illustrates the simple truth that talented researchers in the region tend to be among the most likely in the world to look for opportunities elsewhere.

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And yet, the report suggests, this need not be a disaster for Africa. ¡°Although a country or institution may lose some of its best scientific talent (especially for graduate training), many researchers come back with stronger skills, strengthening collaboration ties between the countries and institutions and improving the quality of their research,¡± it says.

Even when talented researchers do emigrate for good, they often retain strong ties to their home country, it adds, resulting in a flow of ideas across international borders and opening up pathways for training and development for other African researchers.

But just as this outflow of talent may not be all bad, so the World Bank report also highlights that the inflow of talent to Africa from elsewhere isn¡¯t necessarily as helpful as one might assume.

The problem it identifies is that, in the case of sub-Saharan Africa for example, half of researchers are ¡°non-local and transitory¡±: that is, they are from overseas and stay for less than two years.

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While bringing talent into the region, the report warns that such brief comings and goings could ¡°prevent researchers from building relationships with African firms and governments, reducing the economic impact and relevance of research¡±.

One of the study¡¯s other conclusions is that Africa¡¯s mobile researchers are more productive and turn out better research than those who stay put. This is far from being a uniquely African phenomenon, however, and in our news pages this week, we analyse the level of researcher mobility in countries around the world, working with Elsevier to pinpoint the countries that have the highest and lowest levels of mobility, both in and out.

In the UK, if you¡¯re wondering, 71 per cent of researchers are internationally mobile under the criteria set for the analysis. And amazingly, that doesn¡¯t even put it in the top 10 globally.

The analysis paints a fascinating global picture, and what¡¯s clear is that researchers are moving and collaborating across borders for a huge variety of reasons. It also serves as a reminder of how damaging it would be for the UK to withdraw from the world either symbolically, by leaving Europe, or through the increasingly narrow-minded attitude to immigration.

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john.gill@tesglobal.com