Keep in mind that the number does not indicate a 48 percent market share for the Mac operating system, the number represents percent increase.  The data used in this post has been obtained from market research firm Net Applications (Market Share).  The total Mac OS X market share percentage for February 2007 comes in at 6.38 percent.  Based on this data, the following observations can be made:

Percent Increases

• Up 48.0 percent since February 2006
• Up 89.3 percent since February 2005
• Up 81.3 percent since April 2005 (Mac OS X Tiger launched April 29, 2005)

The February 2007 data shows an acceleration in the year-over-year growth versus the three most recent months (the number in parenthesis is the year-over-year growth for the respective month):

• January 2007 (47.7 percent)
• December 2006 (30 percent)
• November 2006 (31 percent)

The following is a view of Apple's Mac OS market share month by month for calender year 2007.  Note that Net Applications splits Mac operating system data into two groups, Mac OS and MacIntel.  MacIntel represents Intel builds of the Mac OS X operating system.  The February 2007 data can be found here.

Observe that Mac OS is shown to have 4.29 percent operating system share while MacIntel is reported to have 2.09 percent market share.  (Internet Explorer users may have difficulty viewing the images.  If so, click 1, 2, 3).  You can click on each image to get a larger view:

Note that the February 2007 Mac OS data (represents PowerPC builds of the Mac operating system) fell by 1.2 percent versus the January 2007 data.  This metric is likely demonstrating that either existing PowerPC Mac users are moving to new Intel-based Macs or that usage of those systems is on the decline.  The March 2007 data will be analyzed to see if a trend can be identified.

Commentary
The first two months of calendar 2007 continue to show strength in the growth rate of the Mac operating system.  Apple's OS market share is clearly on an upward trajectory with no signs of loosing momentum.  The Mac operating system has experienced year-over-year growth in seven of the past eight months dating back to July 2006.  I expect that the Apple will continue to experience market share gains during 2007 and I anticipate that the rate of growth will accelerate following the release of Mac OS X 10.5 Leopard.

Mac OS X Intel Posts 11.2 Percent Increase from January 2007
The data shows that Mac OS X Intel experienced a 11.2 percent increase as it's share rose from 1.88 percent in January 2007 to 2.09 percent in February 2007.  This was below the 23.7 percent increase from December 2006 to January 2007.

The following shows the growth of MacIntel since June 2006 as measured by Net Applications: