"The number of migrants in the world today, both legal and illegal, is thought to total perhaps 200m (though many of the figures, even those used by governments, are at best educated guesses). That sounds a lot, but it adds up to only 3% of the world's population, so there is great potential for growth."
I would have thought this number to be much higher: Far more than 3% of my friends now life in a different country than they were born in. However, it turns out my sample is skewed:
Switzerland has the second-highest foreign-born population percentage in the world. Similarly, San Francisco is a destination for many born outside the US.
Another interesting map from this issue:
While this map just a qualitative view, it seems like the cliche of the rich Western states is still alive. Count the directions of arrows: East to West: 12, vs. West to East: 6. Similarly, South to North: 10 vs. North to South: 3.