Netmarketshare's monthly updates on the state of the operating system and browser markets are useful not because the numbers are accurate — they clearly have a margin of error — but because they show trends. The most obvious trend at the moment is the decline of Microsoft's ancient Windows XP. This enables us to project how long it will be before Windows XP finally disappears, and you're welcome to have a go in the comments below.
The first question is, "What does 'disappear' mean?" There will clearly be a rump of Windows XP users for a long time. There are, after all, still a few people using Windows 98 (0.01 percent) and Windows 2000 (0.03 percent).
We could, perhaps, take Linux's market share as a baseline for something that hasn't disappeared. Linux now has a market share of 1.68 percent, which is still quite a bit below Windows Vista (3.05 percent). Under the circumstances, you could argue for 1.5 percent, because anything less popular than Linux must be irrelevant.
On Netmarketshare's numbers, Windows XP was level with Windows 7 two years ago, and the two operating systems have since diverged. The rot really set in a year ago, in July 2013, when Windows 7 was on 44.49 percent and XP on 37.19 percent, only 7 percentage points behind. Since then, XP has tumbled to 24.82 percent in the latest numbers, July 2014, while Windows 7 has climbed to 51.22 percent.
Windows 7 now has more than twice as many users as XP, and the gap is undoubtedly going to get bigger.
At the current rate of decline, XP should be down to about 12 percent in July 2015, and zero by July 2016. But I expect XP to stay above that level for a very long time. It still has users due to government incompetence, and governments can be amazingly slow to achieve even simple IT tasks. It has a few ageing users who are not interested in buying new PCs and may not even know that XP support has been discontinued. It still has a following among the ignorant and/or recalcitrant, who either don't know or won't admit that Windows 7 is far superior. Finally, it still appeals to pirates, particularly in Asia, who don't mind using pre-Trojanned copies of Windows as long as they're free. Add those together and I reckon XP could bottom out at around 5 percent, which is only a bit higher than Mac OS X 10.9 (4.12 percent).
My guess is that Windows XP will still be around 16 percent in July 2015, where it might still be ahead of Windows 8.x, and around 8 percent in July 2016, though 14 percent/6 percent would not be a surprise.
A really potent virus, or a significant hack, might drive the numbers lower, though perhaps web developers could help.
One of the drawbacks that results from Windows XP sticking around is that it is artificially extending the life of three aged browsers: Internet Explorer 6, 7 and 8. If websites stopped supporting them, it might encourage a few more people to upgrade.
As things stand, IE8 is still the world's most popular browser: it has 21.56 percent of the market, according to Netmarketshare. I suspect most of those come from the 24.82 percent who are still using Windows XP. If so, Google's attempt to capitalize on Microsoft's attempt to kill off XP has been a miserable failure.
With XP visibly declining, this would be a good time for everyone to let it go.