KentuckyFC writes "The remarkable growth of mobile phone use is transforming many parts of Africa. In Sudan and Gabon, more than half of all adults use their phones to transfer money, the activist website Ushahidi used text messages to map post-election violence in Kenya in 2008 and in Nigeria, mobile music services are a multi-million dollar industry. Now demographers have used the way people purchase airtime to map wealth in Cote d'Ivoire on Africa's west coast. They analysed a dataset from one of the country's largest mobile operators containing caller IDs, the cell towers used for each call and the time and amount of all airtime purchases. The researchers say an individual's airtime buying habits are a good proxy for his or her income. As a result, they were able to to map wealth across the entire country. Their map clearly shows the wealthy cities such as Abidjan, the largest seaport in West Africa. But it also shows an unexpectedly wealthy region in the conflict-ridden area that borders Liberia. This wealth probably arises from illegal activities on the border, such as drug, arms and human trafficking, they conclude."