A car, loaded with household wares, drives up a bridge at the Orile-Iganmu district of Lagos
A car, loaded with household wares, drives up a bridge at the Orile-Iganmu district of Lagos August 29, 2013. With between 15 million and 21 million people - the upper estimate is the official one, though no one really knows - and generating a third of GDP for Africa's second biggest economy, Lagos has become almost as alluring to yield-hungry investors as it is to the 4,000 or so economic migrants who turn up each day. But it faces a daily challenge just trying to keep up with the pace of population growth, much of it on the edge of water. Nigeria, already pushing 170 million people, will be home to 400 million by 2050, making it the world's fourth most populous country, according to the global Population Reference Bureau (PRB). Lagos will have roughly doubled in size by then, Fashola and demographers agree. Picture taken August 29, 2013. To match Insight LAGOS-MEGACITY/ REUTERS/Akintunde Akinleye (NIGERIA - Tags: SOCIETY BUSINESS EMPLOYMENT)