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 percent, up over a percentage point, while Gartner had Apple accounting for 12 percent 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.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is email@example.com.
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Correction: This article as originally posted contained incorrect sales data. The story has been amended.