Even though tablet growth has slowed, there will still be growth through 2018, at least globally. "All told, we expect the tablet market to continue to grow, but at a much slower rate than once predicted," Mainelli said.
"Strong demand for Apple's new larger-sized iPhones means the vast majority of consumers' tech spend in the second half of 2014 [in the U.S. and Western Europe] will go toward refreshing phones rather than tablets," he added.
Mainelli also said that IDC had once envisioned a three-year life cycle for tablets, dating back to when the first iPads were introduced in 2010. "But the reality is clearly longer as these devices -- moreso than other consumer electronics -- are typically handed down within a house.... Very few high-quality tablets are retired, with many staying in service...well beyond three years. The result is a swelling installed base and a lack of motivation to buy new products."
In other words, iPads essentially last too long. "When sub-$99 tablets get to be decently usable, we might well see consumers in mature markets with multiple tablets per person," Mainelli added.
Android tablets from a range of manufacturers, with some priced well below $100, will account for 65.7% of the global market this year, though that share will decline after that, even as the total volume of Android tablets grows, IDC predicted. For 2014, iPads will hold 28.9% of the global market, dropping to 26.6% by 2018, while Windows will grow from 4.9% to 11% by 2018, IDC said.
IDC predicted 233 million tablet and 2-in-1 shipments for all of 2014 globally, growing to 303 million in 2018. Gartner pegged tablet sales at 229 million this year, rising to 273 million in 2015.
In addition to the longer refresh rate, tablets represent a transition in how people use computers that are subject to fads and adjustments to newer devices, even smartwatches, analysts said.
"Tablets won't go away, but the initial surge is mostly over and now tablets will behave much more like traditional computers than as the 'must have' new device," said Jack Gold, an analyst at J. Gold Associates. "Users will have multiple choices to make and will pick a tablet based on need and not just because they're cool."
Rob Enderle, an analyst at Enderle Group, said the tablet's useful lifetime is probably up to five years, and with the emergence of smartwatches alongside smartphones and laptops, he said tablets are the "most exposed" to declines in growth "because they are an in-between product."
Enderle also posited another interesting, if questionable, theory on why tablet growth is declining: the passing of Steve Jobs.
"Steve Jobs was the primary promoter of the tablet platform and no one has yet full filled his role since his departure," Enderle said. "Without active, effective promotion in this tablet segment, which wasn't very popular before Jobs, the segment appears to be returning to its roots."
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