Microsoft's own numbers suggest declining Windows market share

Last summer, Microsoft announced that it had sold 175,000,000 Windows 7 licenses through the end of June 2010. Cranking together a few numbers produced some surprising results, which I talked about in my July 26, 2010, article "Do the math: 175 million copies of Windows 7 isn't that impressive."

Last Friday, Brandon LeBlanc said the following on the Windows Team Blog: "18 months ago to this day was when we launched Windows 7 and with that we've hit another important milestone: we are pleased to announce that Windows 7 has sold more than 350 million licenses. The momentum we've seen and continue to see with Windows 7 is incredible." Fair enough. Let's do the math once again.

Microsoft released Windows 7 on Oct. 22, 2009. On June 30, 2010, the company claimed it had sold 175 million copies. On April 22, 2011, Microsoft pegged the number at 350 million. As I explained in my July 26 article, worldwide PC shipments between Oct. 22, 2009, and June 30, 2010, ran about 215 million machines, give or take a bit, based on Gartner's numbers. (IDC's numbers are just a touch lower.) Rifling through Gartner's press releases over the past year, I come up with a total of 266 million PCs and Macs sold between July 1, 2010, and March 30, 2011. Taking 9 percent off that total for Mac sales and adding a proportional amount to fill in the gap from April 1 to 21 of this year, I figure total worldwide PC sales between July 1, 2010, and April 21, 2011, came in around 260 million machines, give or take a few percent.