Shipments of notebooks in first-quarter 2014 were better than expected due to the commercial PC refresh cycle and Windows XP migration. However, shipments of tablets at 56 million declined on year for the first time. Many brands reported weak tablet shipment results in the first quarter due in part to delayed launches of new products. As a result, DisplaySearch said it has lowered its forecast for tablet shipments in 2014 to 285 million.

"Tablet demand in 2014 is being affected by falling demand for the 7-inch class in emerging regions and in China, where many local white-box brands have experienced lower-than-expected shipment growth," said Hisakazu Torii, VP of smart application research at DisplaySearch. "Most major vendors have recently reduced their business plans for 2014. There is a risk that the replacement cycle for tablets will lengthen beyond the one to two year range unless brands can develop more attractive usage scenarios."

For the past several years, tablets and smartphones have been the primary growth driver in the smart device category. In 2014, the on-year growth rate of tablets will fall to just 14% and by 2017 will slow to single digits.

DisplaySearch added that it expects competition between 5.5-inch and larger smartphones and 7- to 7.9-inch tablets will reduce demand for tablets through 2018. Unit share for 7- to 7.9-inch tablet displays peaked at 58% in 2013, but it will gradually decline in 2014 and beyond. Major vendors are likely to move to larger sizes, and shipments of 8- to 10.9-inch tablets will overtake 7- to 7.9-inch tablets by 2018. In addition, DisplaySearch said it expects 11-inch and larger tablets will exceed 10% of the market by 2018. "The increase in screen sizes will help increase tablet PC revenues." Torii said.