Facebook possesses a startlingly massive trove of data on global migration patterns. It's hidden, innocuously enough, amid two simple biographical details that many people post on their profile pages: Where you live, and where you're from.
Between those two data points – spread across the millions of its 1 billion users who volunteer this information – Facebook can paint a picture of where large population shifts take place, which cities seem to attract the most people, and what kinds of communities are losing them.
Facebook's Data Science team recently produced an interesting analysis of what it's calling "coordinated migration" patterns among large groups of people who tend to flock from one city to a common destination (think Warsaw to Chicago, Havana to Miami, or from just about anywhere in Turkey to Istanbul). The results require a grain of salt: Facebook's sample admittedly self-selects for people anywhere in the world who use computers, and as Wired points out, the company's in-house analysis is not exactly open for peer review.