PAYING for a taxi ride using your mobile phone is easier in Nairobi than it is in New York, thanks to Kenya’s world-leading mobile-money system, M-PESA.  Launched in 2007 by Safaricom , the country’s largest mobile-network operator, it is now used by over 17m Kenyans, equivalent to more than two-thirds of the adult population; around 25% of the country’s gross national product flows through it. M-PESA lets people transfer cash using their phones, and is by far the most successful scheme of its type on earth. Why does Kenya lead the world in mobile money...more