(Telecompaper) Global tablet sales are set to increase just 2.1 percent in 2015, with 234.5 million units shipped compared to 229.7 million in 2014, according to a report from IDC. The forecast comes a month after IDC reported the first year-on-year decline in worldwide tablet shipments in the fourth quarter of 2014. The researcher again blamed the increasing popularity of phablet-sized smartphones for its scaled-back sales estimate. In terms of platforms, Android is set to retain close to two-thirds of the market over the course of the 2015-19 period, but its market share will drop to 62.9 percent in 2019 from 67.3 percent last year, said IDC. This year, the report predicts that sales of Android-powered tablets will grow marginally from 154.7 million to 158.1 million. However, iOS tablets are set to fall from 63.4 million units sold last year to 60.1 million in 2015, with Apple's market share dropping from 27.6 percent in 2014 to 23.0 percent in 2019. Windows tablet shipments, on the other hand, are set to grow from 11.6 million in 2014 to 16.3 million this year, before soaring to 38.0 million in 2019, according to IDC.