Google's Android and Apple's iOS will help drive 53.5 million tablet shipments in 2011, according to IDC. But the research firm adds that consumers don't want to be saddled with cellular data plans — and they apparently aren't much interested in tablets running Microsoft Windows, either.

IDC is raising its previous projection of 50.4 million units for the year to 53.5 million, despite first-quarter tablet sales that dropped 28 percent sequentially. Demand fell due to economic concerns, but new product introductions should boost shipments for the rest of the year, the research firm says.

Sales of Apple's iPad 2 (above) have been constrained but are now easing

Apple's iPad (above) holds a comfortable lead over other vendors, though shipments were below expectations for the quarter, apparently due to supply constraints. (iPad 2 supplies have now eased, at least according to Apple's online store, which was recently quoting shipment times from one to two weeks, but now cites delays of just three to five days.)

Nonetheless, Android shows clear signs of establishing a foothold in the tablet market, with the operating system present on 34 percent of devices. But, IDC added, the strategy of tablets via carriers isn't gaining traction among consumers.

No mention was made of tablets running Microsoft Windows, the sales of which appear to be mostly to enterprise customers rather than consumers. (That will likely change, however, when Microsoft releases its more tablet-oriented Windows 8 next year.)

Bob O'Donnell, IDC's vice president of clients and displays, stated, "Like the PC market, media tablets had a bit of a challenging quarter in Q1, as concerns about general macroeconomic issues and the post-holiday letdown took a toll on demand. We expect the rest of the year to be much stronger, but we believe vendors who continue to focus on the telco channel for distribution will face serious challenges."

Despite that toxic combination of lowered consumer demand, dampened economy and supply-chain constraints, IDC believes that the tablets slated to hit the market in the second half of 2011 will prove competitive. "The market will sell close to 53 million units for the year and continue to grow long-term," wrote IDC Research Analyst Jennifer Song.

Other analysts seem to agree on other tablet manufacturers' weakness relative to the iPad.

In a July 7 research note issued by Canaccord Genuity, analyst T. Michael Walkley and his co-authors suggested that the iPad 2's price point is making it difficult for rival tablets to compete in a profitable way. "Our checks indicate both the Motorola Xoom and RIM Playbook have not sold well at current price points, as we believe competing tablets must sell at a substantial discount to the iPad 2," they wrote.

Their research note estimates Apple's share of the tablet market at 56 percent in 2011, followed by Samsung with 12 percent, and Asus with two percent. LG Electronics, Motorola, and Research In Motion are all given three percent of the market, followed by HTC with two percent.

Although Amazon has yet to release a tablet, the Canaccord Genuity note forecasts its 2011 share at five percent. Nor do those predictions change much for 2012, although Apple loses five percent of its overall share to rival manufacturers.

During a June 6 presentation at Apple's Worldwide Developers Conference, company executives claimed that more than 200 million devices running iOS, including the iPad.

The e-reader market also saw a sequential decline to 3.3 million units for the first quarter, though that was more than double the amount shipped a year earlier, according to IDC. Shipments of e-readers will rise 24 percent to 16.2 million units in 2011, according to the research firm.

Nicholas Kolakowski is a writer for eWEEK.

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