August data released yesterday from The Nielsen Company, confirms what research firms and observers have been asserting for months: that Android is now the most popular smartphone operating system.

Nielsen reports that Android was the top choice among people who bought a smartphone in the past six months, while Blackberry RIM and Apple iOS are in a statistical dead heat for second place among recent buyers. Among all smartphone owners, Blackberry still clings to its lead with 31 percent of the market, the firm says, though its edge over Apple, with 28 percent, is slipping while Google's Android is gaining rapidly, now with 19 percent of smartphone users.

Given that the BlackBerry OS 6 update was greeted with lackluster reviews and the wait for the forthcoming OS refresh with the Playbook tablet remains uncertain, RIM's window of opportunity to stop the erosion of market share may be closing. In addition to encroachment from consumer devices like iPhone and Android-based smartphones, Microsoft is preparing to introduce the first Windows Phone 7 devices next week.

The Nielsen figures are in line with the US smartphone market share data  released this week by measurement firm comScore, which reported RIM's share among US smartphone subscribers dipped to 37.6 percent by the end of August, down from 41.7 percent three months earlier. Apple's share held nearly steady at 24.2 percent, while Google's Android climbed from 13 percent at the end of May to 19.6 percent by August.

Microsoft continued to slip, accounting for 10.8 percent of smartphone subscribers, down from 13.2 percent, while Palm rounded out the top five, down only slightly to 4.6 percent. Despite losing share to Google Android, most smartphone platforms continue to gain subscribers as the smartphone market overall continues to grow, the firm notes. The total number of smartphone users in the US rose 14 percent to 55.7 million during the three months ending in August.