How are Windows 8 sales? Still too early to tell

How many people are using Windows 8 one month after its launch? That depends on who you ask and on how closely you look at the numbers.

The most recent stats come from Net Market Share, whose November report was released over the weekend. The cumulative number for the month says 1.09% of all web traffic from the analytics firm's network (160 million visits per month; the exact methodology is here).

But that 1.09% figure is slightly misleading, because it represents aggregate traffic for the month. Net Market Share also tracks web usage on a weekly basis. Here are the Windows usage stats, worldwide, for the period after the Windows 8 launch on October 26:

Windows XP and Vista show consistent negative trendlines, with both Windows 7 and Windows 8 on the uptick.

In the second half of the month, which included the U.S. Black Friday selling period, Windows 8 usage spiked 30 percent.

That's a slightly more positive story than the one told by NPD, which released a study of PC sales based on a four-week survey in the U.S. ZDNet's Mary Jo Foley covered the numbers in a story that suggested Windows 8 sales on new PCs are "off to a slow start with consumers in month one":

Desktop sales are down nine percent compared to a year ago; notebook sales are down 24 percent compared to a year ago.

There are two big troubles with the NPD numbers, though.

First, they don't actually represent month one. NPD's release says "Windows 8 initial four week launch sales include the time period of October 21 – November 17, 2012." That survey period starts five days before the launch of Windows 8 and runs for 22 days after the launch event. It also doesn't include Black Friday. The press release might have been released a month after launch, but the numbers represent sales from the first half of November, traditionally the slowest time of the year.

Second, although the NPD press release stated that "Windows 8 tablet sales have been almost non-existent," the research firm failed to count sales of Microsoft's Surface RT, which was the only tablet on the market for much of the post-launch period.

Finally, there's StatCounter, a rival of Net Market Share, which calculated that by November 26, worldwide web usage from devices running Windows 8 was equal to 1.31% of total traffic. Remarkably, that figure is identical to Net Market Share's calculation.

Trying to turn those usage stats into hard numbers is an exercise in fuzzy math, but it's reasonable to assume that at least half of the 40 million licenses Microsoft sold in the month after Windows 8's launch are now in the hands of computer users. And many new PC models are just beginning to hit the market. NPD says only 58% of PCs sold in their sample period were running Windows 8, with the remaining 42% consisting of inventory running Windows 7. That means the numbers at the end of December will be significantly more illuminating.

Microsoft's business model is based on selling 20 million PCs a month. Interestingly, a 2009 report from NPD on the launch of Windows 7 indicates that "January traditionally has a bigger sales footprint than October." Coincidentally, that's when retail shelves should be fully stocked with new Windows 8 PCs, and it's also when Microsoft is launching its Surface Pro.

In other words: Still too early to tell.