Data source: Net Applications

Windows 7 sold well during the 2009 holiday season, and the results are showing up, not only in sheer revenue, but in the OS market share numbers as well. Nevertheless, in December 2009, Linux was the only operating system to show positive percentage growth in market share.

Between November and December 2009, Windows market share dropped 0.31 percentage points (from 92.52 percent to 92.21 percent), Mac OS dipped 0.01 percentage points (from 5.12 percent to 5.11 percent), and Linux edged forward 0.02 percentage points (from 1.00 percent to 1.02 percent).

Strong sales from Windows 7 and Snow Leopard were not enough to stop both Windows overall and Mac OS overall from dropping. When putting this into perspective across the whole year, though, we see that Windows was actually sliding steadily throughout 2009 (93.66 percent in January 2009), while both Mac OS (4.71 percent in January 2009) and Linux (0.90 percent in January 2009) have been gaining.

You can see the market share pie for December 2009, according to Net Applications, at the top of this post. The graph directly above this paragraph shows how things at Ars are different from those elsewhere, but the differences aren't as significant when it comes to the browser market: our Mac OS share is more than five times greater than the rest of the world, while Linux is six times more. Nevertheless, more than half of our users are on Windows.

Data source: Net Applications

Even if Windows is slowly losing share, Windows 7 is doing phenomenally well. Above, you can see how quickly the OS has been gaining share in its first few months compared to Windows Vista's first few months.

While Vista was at 0.93 percent after a month, Windows 7 was at 4.00 percent; when Vista jumped to 2.04 percent after two months, Windows 7 hit 5.71 percent.

There are many reasons for this, including the fact that Vista had to compete with XP, which was on the market for an abnormally long time. Furthermore, Windows 7 arrived in time for holiday sales, while Vista did not. In addition, Windows 7 had a very successful beta program, both private and public. Most importantly though, Microsoft managed to generate the kind of hype around Windows 7 that it hasn't generated around any of its operating systems in years.

Data source: Net Applications

In terms of OS versions, Windows saw the following changes between November and December: Windows XP dropped 1.28 percentage points (from 69.05 percent to 67.77 percent), Windows Vista dropped 0.68 percentage points (from 18.55 percent to 17.87 percent), and Windows 7 gained 1.71 percentage points (from 4.00 percent to 5.71 percent), meaning it has passed all versions of Mac OS. Speaking of which, Mac OS saw the following progress: version 10.4 dipped 0.04 percentage points (from 0.84 percent to 0.80 percent), version 10.5 dipped 0.14 percentage points (from 2.61 percent to 2.47 percent), and version 10.6 moved up 0.22 percentage points (from 1.38 percent to 1.60 percent).

Taking the historical perspective, we can see that Windows Vista and Windows 7 together have just over a third of Windows XP's market share, while Mac OS 10.5 and 10.6 together have more than five times the market share of Mac OS 10.4.

Before the end of 2010, we're expecting to see Windows 7 pass Windows Vista, Windows XP to drop below the 50 percent mark, and Mac OS X 10.6 to pass 10.5 and 10.4 combined.