Over the next generation, Sub-Saharan Africa faces three big, inter-related challenges. Its population will double to 2 billion by 2045. By then, more than half of Africans will be living in cities. And this group of mostly young people will be connected with each other and the world through...

State failure takes many forms. Somalia offers one extreme. A collapse of central authority as the outcome of a prolonged civil war, where authority descends into competing factions -- headed by warlords -- around the spoils of local commerce, power and international aid. At the other end of the...