Source of Graphic: https://www.netmarketshare.com/operating-system-market-share.aspx?qprid=10&qpcustomd=0
It should be noted that Microsoft stopped supporting Windows XP almost 2 years ago. As a result, Windows XP has become a huge target for hackers, viruses, and the like.
Windows 10 is now the 2nd widest used OS on PCs. However, this is not surprising given Microsoft's aggressive strategy to get people to update those old PCs. See article below.
Now that Microsoft is forcibly downloading Windows 10 onto unsuspecting Windows 7 and 8.1 users’ PCs there’s going to be a lot of unhappy customers faced with a new OS they never asked for nor wanted.