Samsung was the most popular handset maker with a 22.4% market share and Research In Motion was the leading smartphone platform with 41.7%, according to comScore's May report for U.S. Mobile Subscriber Market Share.

The firm, which measures digital trends, based its findings on mobile device usage among 234 million Americans ages 13 and up. The report also found that 49.1 million people in the U.S. owned smartphones during the three months ending in May, which is up 8.1% from the previous period.

One of the more notable findings was the continued traction of Google's Android platform-up 4 percentage points to catch a smartphone subscriber base of 13%, when the other four platforms in the top five were down. By contrast, in February, Google had a 9% share, said Andrew Lipsman, senior director of industry analysis. Additionally, "it jumped from 2% to 13% in a year … for the corresponding period. That's a really significant market share gain,'' said Lipsman. "That's a reflection of the fact that you have several Android-enabled devices, so it's able to gain traction on a lot of different fronts."

RIM's share decreased from 42.1% from the February report, followed by Apple, with a 24.4% share (down from 25.4% in February), and Microsoft with 31.2% (down from 15.1% in February). Palm was ranked fifth with 4.8% (down from 5.4% in February). Most smartphone platforms continue to gain subscribers as the smartphone market continues to grow, even though they are losing share to Google Android, the report said.

The iPhone's decreased share was a "temporary blip" due to the fact that consumers were waiting for the iPhone 4 launch, Lipsman said. "We've seen historically that there are significantly higher gains in subsequent months after a new iPhone launch, so expect to see that happening over the next few months when people get the iPhone 4 in their hands,'' he said.

Besides Samsung, which increased market share by one percentage point from February, the others in the top five for OEM market share were LG, with 21.5% share (down from 21.7% in February), Motorola, 21.2% (down from 22.3% in February), RIM, with a 0.5% increase at 8.7% and Nokia, with 8.1% (down from 8.7% in February).

Among the May report's other findings were that mobile subscribers increased their use of text messaging to 65.2%, up 1.4% from the previous three month period, and browser usage increased as well, up 2.3 percentage points to 31.9% of U.S. mobile subscribers. Application download activity was also on the rise, up 2.1 percentage points to 30 percent of the mobile audience from the previous period. There was significant growth among U.S. mobile subscribers who accessed social networking sites or blogs, the report said, an increase of 2.6 percentage points from the previous period to 20.8%.