Worldwide tablet shipments are expected to reach 221.3 million units in 2013, down slightly from a previous forecast of 227.4 million but still 53.5 percent above 2012 levels, according to IT research firm IDC's Worldwide Quarterly Tablet Tracker.
The tracker, which provides market size, vendor share and forecasts for hundreds of technology markets from more than 100 countries around the globe, predicted shipment growth of tablets will to slow to 22.2 percent year over year in 2014 to a total of 270.5 million units.
The firm forecasted that tablets running Google's Android operating system will constitute 60.8 percent of the worldwide market in 2013, a figure that would slide back to 58.8 percent by 2017.
Apple's iOS tablets, including the iPad Air and the iPad mini, are projected to represent 35 percent of the market in 2013, and that share is forecast to fall to 30.6 percent by 2017.
"In some markets consumers are already making the choice to buy a large smartphone rather than buying a small tablet, and as a result we've lowered our long-term forecast," Tom Mainelli, research director for tablets at IDC, said in a statement. "Meanwhile, in mature markets like the U.S. where tablets have been shipping in large volumes since 2010 and are already well established, we're less concerned about big phones cannibalizing shipments and more worried about market saturation."
By 2017, annual market growth will slow to single-digit percentages and shipments will peak at 386.3 million units, down from the previous forecast of 407 million units. The report noted that Windows-based tablets are not expected to steal share from tablets running iOS and Android until the latter part of the forecast.
"For months, Microsoft and Intel have been promising more affordable Windows tablets and 2-in-1 devices," Jitesh Ubrani, research analyst for IDC's Worldwide Tablet Tracker, said in a statement. "This holiday season, we expect a huge push for these devices as both companies flex their marketing muscles; however we still don't expect them to gain much traction. We're already halfway through the holiday quarter, and though there have been some relatively high-profile launches from the likes of Dell, HP, and Lenovo, we've yet to see widespread availability of these devices, making it difficult for Windows to gain share during this crucial period."
The rise of large phones, often referred to as "phablets," could well push consumers back toward larger tablets as the difference between a 6-inch smartphone and a 7-inch tablet isn't great enough to warrant purchasing both.
Apple's launch of the iPad Air, a much thinner and lighter version of its 9.7-inch product, could herald another market transition back toward larger screens, reversing the trend toward smaller tablet devices the market has seen for the past two years.