Please note that this does not mean that Apple's market share is 31 percent.  The number represents percent increase.  Data used in this post has been obtained from market research firm Net Applications (Market Share).  The total Mac OS X market share number comes in at 5.67 percent for the month.

Based on the firm's calculations the following metrics can be calculated.

Key Percent Increases

The December 2006 Key Percentages outpaced the growth reported for November 2006 which were as follows:

Below is an updated view of Apple's Mac OS market share month by month for calender year 2006 up to and including December 2006.  Pay careful attention to the numbers because Market Share splits Mac operating system data into two groups, Mac OS and MacIntel.  MacIntel represents Intel builds of Mac OS X Tiger.  Have a look at the December 2006 data.  Mac OS is reported to have 4.15 percent of the operating system share while MacIntel is reported to have 1.52 percent operating system market share.  When the numbers are combined, we get the following

(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:

 

Mac OS X Intel Posts 17.8 Percent Increase In One Month
The data shows that Mac OS X Intel experienced a 17.8 percent increase as it's share rose from 1.29 percent in November 2006 to 1.52 percent in December 2006.  This outpaced the 15.2 percent increase from October 2006 to November 2006.

Growth Continues and Accelerates
The OS X market share numbers show that December marked a return to market share acceleration on a monthly basis.  Note that November experienced a slowdown so the reversal is a positive sign for Apple's upcoming Q1 2007 earnings as the month included the holiday buying season.

About Market Share
The following is taken from the Net Applications site:
"This data provides valuable insight into significant trends for internet usage.  These statistics include monthly information on key statistics such as browser trends (e.g. Internet Explorer vs. Firefox market share), search engine referral data (e.g. Yahoo vs. MSN vs. Google traffic market share) and operating system share.

We use a unique methodology for collecting this data.  We collect data from the browsers of site visitors to our exclusive on demand network of small to medium enterprise live stats customers.  The sample size for these sites is more than 40,000 urls and growing.  The information published is an aggregate of the data from this network of hosted website statistics.  The site unique visitor and referral information is summarized on a monthly basis"