The Atlantic reports that, in Ivory Coast, the use of cell phones can be used as a proxy to map wealth:
There’s good reason to believe in a connection between airtime purchases and wealth. Mobile service providers throughout Africa allow their customers to transfer minutes between one another. In Côte d’Ivoire, such transfers are especially easy. The result is that airtime is used as currency in Côte d’Ivoire, Ghana, Egypt, and other countries. Airtime goes beyond being a proxy for wealth. In a sense, it is wealth.
Here’s a link to the study done by some Belgian researchers and, below, a map of their findings.
It’s kinda cool, but perhaps also not too surprising. The map basically shows more cellphone use in urban areas and on main roads used for commerce. I wonder if this map would look the same if all you did was chart the amount of people or road traffic.