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[History] 101 years ago the population exchange agreement between Turkey and Greece was implemented. It was one of the biggest resettlements of the early 20th century.
(discuss.tchncs.de)
That's a useful map, actually shows a lot more than the title suggests! I note the arrow showing exodus from Circassia / Abkhazia (pushed by Russia) is at least as big. To complete the picture it could be useful to indicate, alongside the source end of each arrow, a symbol indicating the number who didn't make it due to war and genocide, and for context the numbers who remained. Also there are emigrants who moved outside the region.