Here's a shocker: In December 2013, Windows XP had a 28.98 percent market share, but in January 2014, the share rose to 29.23 percent! 
I fail to understand why people are installing this 13-year old OS, or is it a tracking error by NetMarketShare? 
Windows 7's market share dropped from 47.52 percent to 47.49 percent. Windows 8's share also fell from 6.89 percent in December to 6.63 percent in January because of Windows 8.1 free update. Windows 8.1's share rose from 3.60 percent to 3.95 percent.