The mobile operating system market share numbers are in for Kantar Worldpanel’s last quarter, and the numbers are shocking. Not the Android and iOS numbers: Steady but unspectacular growth for Android and gradual but not catastrophic drops for Apple are pretty much in line with expectations. But the BlackBerry and Windows Phone numbers are dramatic changes from the same quarter a year ago. Windows Phone looks to be finally taking off, with 52 percent growth December, January, and February of this year compared to the same three months in 2012. And BlackBerry is falling of a sales cliff, with an 81 percent plunge in sales. Source: Kantar WorldPanel Smartphone sales by operating system – U.S. The big kahuna, of course, is Android. Google’s Android now owns more than half of U.S. smartphone sales, with 51.2 percent market share. That’s up from 45.4 percent in the quarter a year ago. Meanwhile, iOS is holding fairly steady at number two, with 43.5 percent, down slightly from last year’s 47 percent. What’s interesting about the Windows numbers, even though they are on a much smaller installed base, is that Windows Phone is currently the fastest-growing mobile phone platform. At 4.1 percent of mobile operating system market share, Microsoft still has a very long ways to go, and growth rates could start to slow as it piles up share. But the numbers have to be encouraging for Redmond as it is finally gaining traction in a market that it once appeared to have completely lost. And the international numbers contain pockets of even more good news, such as Italy, where Windows Phone now makes up 13.1 percent of new phone sales. Apple’s mobile offerings are strongest with the two largest U.S. carriers, AT&T and Verizon. Both sell a majority of iOS smartphones, with AT&T selling 68.4 percent iOS versus 20.8 percent Android, and Verizon selling 55.1 percent iOS versus 43.4 percent Android. Meanwhile, Samsung is continuing to expand its Android leadership, taking away market share from competitors LG and HTC: “Of those who changed their phone over the last year to a Samsung smartphone, 19 percent had previously owned a Samsung feature phone, 15 percent owned a HTC smartphone, 14 percent owned an LG feature phone, 10 percent owned a Samsung smartphone, and 9 percent owned a BlackBerry,” said Kantar Worldpanel analyst Mary- Ann Parlato. “It’s apparent that Samsung is successful at capturing users from across the competitor set and not just gaining from their own loyalists.” Kantar Worldpanel is the largest continuous consumer research mobile phone panel in the world, and conducts more than 240,000 interviews per year in the U.S. alone to determine what consumers are buying and using.