Analyst firm IDC has lowered its expectations for the global PC market this year, blaming the drop on the demand for tablet computers, the economy and a bad first quarter.

IDC said that PC shipments are expected to grow by 4.2% in 2011, down from its February forecast of a 7.1% market increase. However, IDC noted that its analysts expect the market to rebound next year and show 10% to 11% growth through 2015.

But even 10% to 11% growth isn't impressive compared to how the market was booming just a few years ago. Consumer PC shipment growth averaged 18.9% from 2005 to 2007, according to IDC. During 2008 and into 2009, consumer PC shipments growth also increased, hitting more than 21%.

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IDC noted that there are several factors tamping down the market. Tablets, such as Apple's iPad and iPad 2 and netbooks to a lesser extent, have been taking a bite out of the laptop and desktop market for several months.

"Consumers are recognising the value of owning and using multiple intelligent devices, and because they already own PCs, they're now adding smartphones, media tablets and e-readers to their device collections," said Bob O'Donnell, an IDC vice president. "And this has shifted the technology share of [people's wallets] onto other connected devices."

The persistence of the sluggish economy, which is affecting housing and employment along with food prices and tight credit, is making discretionary spending harder to come by, IDC said.

"The potential boost to the PC market from thinner designs, longer battery life, instant on, touch, and other improvements will likely not be widely available until 2012, and will have to address price-sensitive buyers in order to drive higher levels of growth," the report noted. "In fact, the appeal of these future enhancements could be seen as another motive for consumers to delay the purchase of a new PC until they are available and to focus on other products in the meantime."

First-quarter PC shipments were down 1.1% from the same period in 2010, according to IDC. However, IDC expects that new PC features, along with an improving economy, should help to boost PC sales next year.

"The PC market has definitely hit a slow patch," said Loren Loverde, an IDC vice president. "Nevertheless, the long term growth drivers, first among which are growth in emerging markets, declining prices and growing functionality, remain intact, and the product and design innovations underway will keep PC growth healthy in the long term."