By Louis Bedigian

After 11 years of growth, sales of PCs -- including notebooks, netbooks and desktops -- are expected to decline.

This revelation comes from three different researchers. In a report by IHS iSuppli (IHS), the researcher showed that worldwide PC shipments will contract this year by 1.2% to 348.7 million units. In 2011, 352.8 million units were shipped.

In another report, IDC found that worldwide PC sales declined by 8.6% in the third quarter. In the United States alone, shipments declined by 12.4%. Gartner (IT) published similar results.

"There was great hope through the first half that 2012 would prove to be a rebound year for the PC market," Craig Stice, a senior principal analyst for computer systems at IHS, said in a company release. "Now three quarters through the year, the usual boost from the back-to-school season appears to be a bust, and both AMD and Intel's third-quarter outlooks appear to be flat to down. Optimism has vanished and turned to doubt, and the industry is now training its sights on 2013 to deliver the hoped-for rebound. All this is setting the PC market up for its first annual decline since the dot-com bust year of 2001."

Gartner concurred with that assessment.

"Retailers were conservative in placing orders as they responded to weak back-to-school sales," said Mikako Kitagawa, a principal analyst at Gartner. "By the end of September, retailers were focused on clearing out inventory in advance of the Windows 8 launch later this month. On the professional side, there was minimum impact from Windows 8 in the quarter because the professional market will not adopt Windows 8 PCs immediately after the release."

"PCs are going through a severe slump," added Jay Chou, a senior research analyst with IDC's Worldwide PC Tracker. "The industry had already weathered a rough second quarter, and now the third quarter was even worse. A weak global economy as well as questions about PC market saturation and delayed replacement cycles are certainly a factor, but the hard question of what is the 'it' product for PCs remains unanswered. While Ultrabook prices have come down a little, there are still some significant challenges that will greet Windows 8 in the coming quarter."

Dell (DELL) and Hewlett-Packard (HPQ) are among the biggest companies enduring declines. In the third quarter, Gartner said, HP declined by 16.4% worldwide, while Dell dropped 13.7%. In the United States, the declines were even greater.

Domestically, Apple (AAPL) suffered as well. While the company released a brand-new version of the MacBook Pro and knocked $100 off the 13-inch MacBook Air, Apple still experienced a decline of 6.1%.

IDC's numbers are nearly on par with Gartner's, but there is one exception: IDC's research shows that Apple declined by 7%.

IHS did not provide any details regarding how individual corporations are performing.

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