Google's Android operating system accounted for 36 percent of U.S. smartphone market share through April, 10 percentage points higher than Apple iOS's 26 percent share for the iPhone.
Research In Motion's BlackBerry OS ranked No. 3 with 23 percent, according to Nielsen, which said 37 percent of mobile consumers now own a smartphone. Windows Mobile took fourth with 9 percent. Throw in another 1 percent for Windows Phone to give Microsoft double-digit smartphone share.
Android passed iOS and BlackBerry in U.S. and world market share late last year, according to Nielsen, comScore, IDC, Gartner and just about any reputable researcher.
However, Nielsen's new data for April shows that smartphone platform growth may be slowing, at least among the top three platforms.
That means Android share jumped 8 points from January through March, but then slipped a point through April to rest at 36 percent.
Nielsen's March count showed iOS grabbing 27 percent and BlackBerry holding down 22 percent, which means iOS and BlackBerry each slipped a point in the researcher's latest count.
Why? It's unclear, though perhaps after blockbuster holiday and early 2011 sales, smartphone sales are in a quiet period.
The Android and iOS slowdown in growth is interesting, considering the availability of the heavily hyped Verizon iPhone 4, and the Android-based Motorola Atrix 4G and HTC ThunderBolt smartphones.
Perhaps this is the beginning of a plateau for the top platforms, presenting a growth opportunity for Microsoft Windows Phone? Perhaps consumers were waiting for the now available Samsung Droid Charge or Samsung Infuse 4G, as well as iPhone 5?
Whatever the case, consumers are still chomping mobile data at a prodigious clip through April, Nielsen said.
The researcher said 74 percent of Android smartphone owners and 79 percent of iPhone owners downloaded apps in the past 30 days. Also, 43 percent of Android owners and 46 percent of iPhone owners streamed online music or mobile radio in the past month.
Nielsen noted that consumers with Android devices consume more data on average. An analysis of nearly 65,000 cell phone bills in the United States found that Android smartphone owners consumed an average of 582MB of data each month, compared to 492MB for iPhone owners.
Those stats are certainly promising for mobile applications makers and Google and Apple, both of which sell mobile ads against the apps on their platforms.