From The Economist:
"Kenya leads the world in mobile money, with more active accounts than adults in its population. The total value of transactions made by mobile phone in 2013 was around $24 billion, more than half the country’s GDP. The leading mobile payment system in Kenya, M-PESA, was launched in 2007. A year later it expanded to Tanzania. While uptake there has not been as strong, the total transaction value is close to that of Kenya. As mobile phones have become more widely available, mobile payment transfers have helped reach the “unbanked”. In at least eight countries, including Congo and Zimbabwe, more people have registered mobile-money accounts than traditional bank accounts."