(Telecompaper) GfK has upgraded its forecast for global smartphone sales, saying it sees stronger sales of mid-range and high-end phones, helping to reverse the trend of sub-USD 100 phones gaining share. It now expects annual sales of USD 425.9 billion, equal to growth of 5 percent from USD 406.0 billion in 2015, compared to a previous forecast for a small fall to USD 400.7 billion. GfK's forecast are based on retail sales, rather than manufacturer shipments as used by most market researchers. GfK said volume growth is coming from many emerging markets, especially a resurgent China, as well as parts of Asia and Africa. Especially consumers in rural areas are driving the demand, it said.