Some of the darkest clouds threatening the global economy have started to lift, according to the World Bank's periodic update to its economic forecasts. In the latest version of the twice-yearly Global Economic Prospects report, the World Bank estimates the world economy grew just 2.3 percent in 2012. It expects growth to pick up only modestly in the coming years, from 2.4 percent in 2013 to 3.3 percent in 2015. Developing countries were responsible for more than half of global growth in 2012, the report said, and they will continue to be an engine of growth. The report estimates that developing countries grew 5.1 percent in 2012, and that the pace of growth will accelerate to 5.8 percent in 2015.