Nicolas Retsinas writes:

The United Nations estimates that, today, 2.8 billion people live on less than $2 a day. And it is this huge, desperate underclass that is filling these mega-cities. Children are more likely to roam in gangs than attend school. Cholera and typhoid – listed as “rare” in Western textbooks – are endemic.

Parts of these cities are modern, with the familiar skyscrapers, highways and BlackBerry-toting workers. Yet they are surrounded by rings of shocking poverty where millions live in paper-covered hovels.

Without some concerted action from nations and international institutions, these mega-cities will grow larger and more desperate. Philanthropy helps, but these developing countries need public policies that promote property ownership, increase access to credit and enhance government transparency.

It took more than 50 years to address the slums of the 19th century. But there is an urgency to today’s task. The slum dwellers of Lagos and Manila and Karachi are part of the global economy, bound to the rest of the world. Their misery will spill beyond their borders, and if that happens, our urban age risks becoming a global nightmare.

Not much new is being said here. The argument is?