Global demand for tablets continued a year-long slide, as shipments fell for the fourth consecutive quarter amid signs of market saturation in North America, Asia and Western Europe, IDC noted in a report released Thursday. Worldwide shipments fell 12.6 percent year-over-year to 48.6 million during the third quarter, according to IDC’s Worldwide Quarterly Tablet Tracker. The installed base of tablets at the end of 2014 was 581.9 million, a 36 percent increase from the prior year, but there are signs that growth will slow down soon.