Adoption of Mac OS X 10.7, also known as Lion, has stalled, according to statistics from online ad analytics company Chitika.
"Lion's adoption rate has been less than stellar, to say the least," Chitika reported in a blog post Friday, citing data that showed Lion was only the third-most-popular of all Mac editions with a 16% share, behind both OS X 10.6 (Snow Leopard) with 56% and 10.5 (Leopard), with 22%.
Chitika claimed that Lion's adoption rate dramatically slowed during September and October, with increases in those months of just one-fourth that of August.
Apple, however, has touted Lion's success several times since its July launch, saying in early October, for instance, that the new operating system had sold 6 million units, nearly double the number of copies sold of Snow Leopard during a similar period in 2009.
But Chitika's numbers are contested by another metrics firm, Net Applications.
The California-based Web measurement company had Lion in second place among all Mac operating systems during October, with a 26.4% share of the Mac market, more than 10 points higher than Chitika. In Net Applications' estimates, Snow Leopard powered 52.1% of all Macs, while Leopard accounted for 16.5% last month.
While Net Applications also noted a slowdown in Lion's adoption pace over the last two months, the growth decline was much less significant than Chitika claimed.
According to Net Applications, Lion gained 4.8 percentage points in September and 4.5 points in October, or about half as much as in August, when Lion jumped by 11.5 points.
Most of the gains by Lion have been made at the expense of Snow Leopard, Lion's precursor. Snow Leopard, which launched in 2007, has lost only about one-fourth as much share as Snow Leopard since July.
That's no surprise, as Snow Leopard made up the bulk of all Mac operating systems prior to Lion's launch, and Apple made it more difficult and expensive for Leopard users to update to Lion. Another contributing factor is that Lion, like Snow Leopard before it, won't run on older Macs equipped with PowerPC processors.
The different results posted by Chitika and Net Applications are likely due to the different ways each collects, then calculates share.
Net Applications, for example, gathers unique visitor data from tens of millions of users each month who visit an estimated 40,000 websites. It also weights the data to account for the relative lack of insight into people browsing from some countries, China included, that have large pools of computer users.
In Net Applications' methodology, each Chinese visitor carries more weight than a corresponding user in the U.S. simply because there are relatively few Chinese users amongst its data. Combined with China's larger Internet-using population, that means one Chinese Mac user can swing the share results more dramatically than can one user in the U.S.
China has been a hotbed for Apple lately: In the quarter ending Sept. 30, China, Hong Kong and Taiwan together accounted for 16% of all Apple's revenues. Chinese buyers have been especially taken with the new MacBook Air, which went on sale there just over two months ago.
The Air, like any new Mac sold in the U.S. since mid-July, is equipped with Mac OS X Lion.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@computerworld.com.