Summary: IDC's growth projection is based on inexpensive Android devices with screen sizes of about 7 inches driving demand. By Larry Dignan for Between the Lines |May 28, 2013 -- 13:37 GMT (06:37 PDT) Tablet shipments are expected to surge and eclipse PC units by 2015 largely due to inexpensive devices with 8-inch screens and smaller, according to research firm IDC. IDC said that it expects tablet shipments to be 229.3 million units in 2013, up 58.7 percent from 144.5 million units in 2012. In 2013, tablet shipments will pass portable PCs and in 2015 outrun the entire PC market. In other words, cheap good-enough computing with a mobile spin is in. The other wrinkle for IDC's growth projection is that Android devices with screen sizes of about 7 inches are driving the surge. IDC said that average prices for tablets will fall 10.8 percent in 2013 to $381. PC prices are nearly double that tally. According to IDC, tablets with screen sizes of 8 to 11 inches will only be 37 percent of the market in 2017, down from 73 percent in 2011. In just two quarters, the iPad mini and Android devices have made smaller tablets dominant.