The survey compared trends in the U.S. mobile-phone industry during the three-month period ending in May, compared to the previous three-month period ending in February. Leading mobile original equipment manufacturers (OEMs) and smartphone operating system platforms were assessed among wireless subscribers aged 13 and older.

Apple Number Two

The company said 49.1 million people in the U.S. owned smartphones during this period, a jump of 8.1 percent over the February period.

RIM's position as the number-one smartphone platform shrank 0.4 percent to 41.7 percent during this period, but it remains way out in front of number-two Apple, whose 24.4 percent represented a one-point drop. However, the May period does not include the June launch of the iPhone 4, which has sold more than 1.7 million units to date. About 11 points down from Apple is Microsoft, at 13.2 percent and the largest drop in this period of any of the top platforms -- 1.9 percent.

Google had the biggest increase -- four percent -- bringing it into fourth place with 13 percent, and Palm's webOS (now owned by Hewlett-Packard) was way down in fifth place at 4.8 percent.

The leading handset manufacturer in the survey was Samsung, with 22.4 percent of mobile subscribers, a one-point increase over the previous three-month period. LG was second with 21.5 percent, with virtually no change, and Motorola was third at 21.2 percent, a drop of 1.1 percent. RIM and Nokia took the bottom places in the top five, with 8.7 percent and 8.1 percent, respectively -- about half a point increase for RIM and slightly more than half a point drop for Nokia.

Text Messaging Still Tops

With the rapidly growing availability of third-party applications for mobile devices, activity is a continually changing picture. The survey found that the most popular activity remained text messaging to another phone, with about 65.2 percent of subscribers engaging in that activity.

Second was using a browser, with 31.9 percent, followed by downloading applications at 30 percent, playing games at 22.5 percent, accessing a social-networking site or blog at 20.8 percent, and last was listening to music on a mobile phone, at 14.3 percent. All activities gained points in this period, ranging from 0.7 to 2.6 percent.

Avi Greengart, an analyst with industry research firm Current Analysis, noted that Android's rise in market share is being built on what was, not so long ago, zero. Now, he pointed out, the platform is sprouting "multiple devices on multiple carriers."

Greengart also noted that, overall, smartphone ownership is increasing, so that even platforms or devices that are relatively stable in their market share are increasing absolute numbers of users.