The World Bank said Tuesday it expects global commodity prices, important for emerging economies, to remain weak through 2016, with resuming Iran exports holding down oil prices. In a new report, the global development institution also forecast that a strong return of the El Nino weather phenomenon, which can affect southern hemisphere food crops, will not force grain prices sharply higher because of large existing stockpiles. The quarterly commodity-sector report found the outlook for commodities to be generally weak amid the slower global economy. "All main commodity price indices are expected to decline in 2015, mainly owing to ample supply and, in the case of industrial commodities, slowing demand in China and emerging markets," it said. Non-energy commodities could gain slightly in 2016, but only after sharp declines this year, the report forecast. Food prices, down more than 15 percent this year, could climb back only 1.5 percent in 2016, it said. The drop in commodity prices has hurt economies of emerging and poorer countries dependent on exports. However, low prices have the benefit of encouraging more consumption and higher industrial output in advanced economies, to spark global growth.