Mobile phones are changing developing markets faster than anyone imagined. Today there are some 3 billion mobile subscriptions worldwide, and that will grow to 5 billion by 2015, when two-thirds of the people on earth will have phones, predicts Finnish handset maker Nokia Corp. Nowhere is the effect more dramatic than in Africa, where mobile technology often represents the first modern infrastructure of any kind. The 134 million citizens of Nigeria, Africa's most populous country, had just 500,000 telephone lines in 2001 when the government began encouraging competition in telecommunications. Now Nigeria has more than 30 million cellular subscribers. Muruguru, meanwhile, had just a single pay phone before people started getting handsets a few years ago. "Communications used to be a barrier," says Paul Ndiritu, the former village head man. Since the advent of mobile phones, he says, "the burden has eased."