In the June 2014 issue of the Newsletter of the European Mathematical Society,there is

an article (by Martin Andler, from Versailles) on the invited speakers at this year’s ICM, and, in particular, on geographical shifts in their career.

Besides offering some tables, the article briefly enumerates a few perspectives on the movement of mathematicians between countries, without really endeavouring to resolve the tensions between them. My aim here will be to give a summary of the situation and what I see as a second step in the analysis of these issues, in part with the hope that readers of this blog will discuss them further.