...is remittances, apparently. Well, that's nonsense. (Apparently the top 100 GDPs in the world also contain a bunch of corporations, game worlds, cities, California, etc. Enough!)
But this is still an interesting-looking piece from Time on migration and remittances:
Waly, a 32-year-old building cleaner, only got to know his father when he sneaked into France at 18 on a boat from Morocco; he now works legally in France. A large photograph hangs above Waly's narrow bed, of his 2-year-old daughter, whom he has never met. The migrant tradition has continued into the next generation, fueled by the same force that kept his father rooted in France for decades — the need to send money home.