(Telecompaper) Worldwide shipments of tablets and 2-in-1 devices are forecast to reach 221.8 million units in 2015, a decline of 3.8 percent from 2014, according to the latest forecast from IDC. The new outlook follows two consecutive quarters of declining sales and represents a modest downward revision from the previous forecast of 234.5 million units and 2.1 percent year-over-year growth in 2015. While IDC expects overall sales to decline in 2015, some products are forecast to experience strong growth, such as cellular-capable tablets and 2-in-1 devices. The latter two products still represent a small portion of the entire market, but are expected to grow at a five-year compound annual growth rate of 5.6 percent. Over the same period, the Wi-Fi-only device market is expected to contract at a CAGR of -0.4 percent. IDC also predicts fewer sales of small-screen tablets, dropping to just under half the market in 2019 as phablets become more popular in the smartphone market. This will also impact average selling prices as larger screen devices tend to cost more.