Apple may finally be feeling the PC sales slump in the US, research firm IDC said Thursday.

According to IDC, Apple sold fewer Macs in the US. during the second quarter than it did in the same period a year earlier. If the research firm's forecast is accurate, the decline would be Apple's first in three years.

IDC estimated that Apple sold 1.81 million Macs in the US during the quarter that ended June 30, down 1.1% from the 1.83 million machines sold in the same quarter of 2011.

"We looked at the sequential movement for Apple, which generally is a good predictor of what to expect," said IDC analyst David Daoud, referring to quarter-by-quarter comparisons as he explained how the PC tracking team came to its forecast. "We believe there will be a normal pattern from Q1 to Q2, but we [lowered Apple's growth] for a number of reasons, including very weak demand in the broader economy."

Apple's first quarter of 2012 was particularly poor when measured sequentially. Mac sales fell off the proverbial cliff after 2011's record-setting fourth quarter, dropping by 22.7% sequentially, the biggest quarter-over-quarter decline in the Mac's history.

Other factors IDC and rival research firm Gartner cited for the contracting U.S. PC business were weak sales to education, uncertainty by consumers about whether they should buy a tablet or a computer, and postponed purchases because of impending operating system upgrades.

The last time Apple's U.S. sales were down year-over-year was in early 2009, when the country was in the midst of its worst economic crisis since the 1930s.

Of course, there's no guarantee that IDC's estimate is on target. Ballparking Apple's U.S. sales, said Daoud, is a "very difficult exercise."

Case in point: Gartner has a different take on Apple's U.S. Mac sales. While it also put the Cupertino, Calif., company in the No. 3 slot on Thursday, behind both Hewlett-Packard and Dell, it set domestic sales at 1.91 million Macs for a 4.3% increase over the 1.83 million sold the year before.

Although the news for Apple may be bleaker than usual, it wasn't nearly as gloomy as what other industry leaders heard from the research firms. IDC said that HP's sales were off 12% and Dell's 9.2% for the quarter, while the overall U.S. PC business contracted by 10.6%. Gartner estimated HP and Dell were down -- 12.7% and 9.5% -- respectively, and that U.S. PC sales fell 5.5%.

So even if IDC's more pessimistic prognostication proves correct, Apple will be able to boast that it beat the PC average for another quarter.

Another positive in both IDC's and Gartner's forecasts of Thursday: Because of the large sales decline overall, Apple gained ground in U.S. market share. IDC said Apple's share of U.S. sales for the quarter climbed to 11.4%, up over a percentage point, while Gartner had Apple accounting for 12% of all personal computer sales during the period.

The notebook refresh of last month, which included the introduction of a MacBook Pro with a higher-resolution "Retina" screen, likely contributed little to the second quarter as the new models were sold only in the last two-and-a-half weeks of the period.

Apple will disclose its second-quarter Mac sales numbers July 24 during an earnings call with Wall Street analysts.


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