The Windows 10 installed base continues to grow at a fast rate, but its actual usage is lagging far behind. That's the takeaway from the latest numbers by Net Applications.

Through its analytics, Net Applications puts Windows 10 usage at around 9% of all PCs, which translates to 148 million PCs. Microsoft hasn't released any new numbers in a while. The last official figure was 110 million around October.

Net Applications acquires its usage data from a network of some 40,000 sensors embedded in websites around the world. It captures data from 160 million unique visitors each month, giving a global usage market share, but not necessarily an installed base market share.

Windows 7 remains the favorite OS, with 56.1%, followed by Windows 8.1 at 11.1% and Windows XP at 10.6%. A deeper look at the Net Apps numbers, though, shows Windows 10's momentum is slowing. It rocketed to 5.2% in the first month after release, then crawled to 6.6%, 8%, and 9% in the ensuing three months.

Meanwhile, Windows 7 ends the year pretty much where it started, at 56% in both January 2015 and November 2015. Windows 8.1 actually rose a tiny bit, from 10% in January to 11.1% in November. Windows XP was the big loser, dropping from 19% at the start of 2015 to 10.6% by November.

So what do we make of all this? Well, the XP numbers tell me a lot of old machines were finally replaced with Windows 10, but the steadiness of Windows 7 and 8.1 means people aren't upgrading all that much. Again, I'll remind you that Net Applications measures use, not installations. I've downloaded Windows 10 twice, on my desktop and laptop, but promptly removed it from the desktop because, quite frankly, I hate it. It's still on the laptop because I should have at least one Windows 10 system for testing reasons.

How many other people did as me: downloaded the free update and either hated it, had problems or compatibility issues, or were put off by the rampant spying and went back to Windows 7 or 8? We don't have a good measure of Windows 10 installs that were reversed, and that number would be more telling than any other.

Now, there has been an interesting new analytics player in the form of the Digital Analytics Program (DAP), which monitors the operating systems of visitors to more than 4,000 websites on over 400 different domains maintained by U.S. government agencies. Its number showed Windows 10 usage in the U.S. was 24% higher than the rest of the world, but since it's monitoring U.S. government websites, the numbers are going to skew to the U.S. anyway.

The same goes for Steam analytics, which gathers OS and other information from people using the Steam app. Steam has, for all intents and purposes, replaced GameStop and other retail outlets for selling PC games. A Best Buy employee even told me they dumped their PC games section because everyone uses Steam. So it's a good measure of consumer use.

And, according to Steam, Windows 10 is up to a 28.8% installed base, while Windows 7 is down to 42%. Windows 8.1 is hovering at 16.5%, and XP is effectively dead at 2.1%.

It shows how hard it is to get an accurate picture of things. Although these numbers come out monthly, the next major stats will be in February. That's when January analytics come out and we see how many new Windows 10 PCs were delivered under Christmas trees.