That really shocked me, too. But it was a credible number, not just because the author is such a careful scholar, but because when I looked up the numbers for specific countries like Ukraine, they were realistic.

Vast numbers of Ukrainians have fled not just to other countries but to parts of their own that at first seemed safer. From the recent news about a supposedly "safer" part like Lviv, you can see why millions of Ukrainians are still displaced either within their country or beyond its borders.