The world's poorest people are now concentrated most heavily in Sub-Saharan Africa after China's huge leap in pulling its citizens out of extreme poverty in recent decades, according to new estimates released Wednesday by the World Bank.

About 1.2 billion people in the world lived in extreme poverty in 2010, subsisting on less than $1.25 a day. That's down from 1.9 billion three decades ago despite a nearly 60% increase in the developing world's population.

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