The global tablet market continues to soar, with Apple on top for the foreseeable future with its iPad, although Android-powered shipments are giving Apple a run for its money. Microsoft's Surface tablets, running two versions of Windows, are slowly catching on.

According to the latest research from Boston-based Strategy Analytics, Apple's iOS devices, the iPad and iPad mini, command a 48 percent "strong leadership Relevant Products/Services position" among the 40.6 million total tablets sold in the first quarter of this year. The number of tablets shipped rose 117 percent from a year ago.

The White-Box Factor

Apple's share is down substantially, however, from its majority share of 68 percent in the first quarter of a year ago. That slippage is mainly at the hands of tablets running Google's Android operating system Relevant Products/Services, made by a variety of manufacturers, the largest of which is Samsung.

Android's share of the market grew from 34.2 percent to 43.4 percent in the same time frame. Microsoft, which had no horse in the race last year, jumped to 7.4 percent of the market in the just-ended quarter with its Surface devices, which run either Windows 8 or Windows RT.

But Android's growth could be even bigger, depending how you look at it.

"Android represented 43 percent market share of the branded tablet market," Strategy Analytics' director of tablets, Peter King, told us.

"But when you added in the white-box market -- budget tablets from Shenzhen -- that figure grew to 52 percent, and iOS slips to 41 percent from 48 percent. So, we believe that certainly for the next couple of years, Apple should worry about Android and not Windows, which will only ever reach the high teens of market share, or BlackBerry, which will never be anything other than niche."

BlackBerry's PlayBook tablet is included in the "other" category in the Strategy Analytics survey, which ranked at a sad 1 percent of the market, less than half its 2.7 percent share last year for smaller players.

"White-box" tablets are those made by a manufacturer that vendors rebrand as their own.

More Variety Expected

King said he expects Apple to increase the range of tablet size and form offerings beyond its current two iPads. But it won't be alone in diversifying.

"We expect to see new form factors from all vendors -- certainly improved Retina minis as well as both smaller and larger sizes," King said. "We can expect to see 8-inch Windows tablets hitting the market quite soon as well."

Looking at shipments, Apple's 11.8 million for the first quarter of 2012 grew to 19.5 million this year, according to Strategy Analytics' estimates, while Android more than doubled its 6.4 million units shipped, with 17.6 million. Windows went from zilch to 3 million units shipped in the beginning of this year.

Windows shipments would be greater, Strategy Analytics said, if not for "very limited distribution, a shortage of top-tier apps, and confusion in the market."