RIM's BlackBerry was the leading mobile smartphone operating system in the US in December 2009 with 41.6 percent share of US smartphone devices. But Apple's iPhone OS ranked second with 25.3 percent share (up 1.2 percentage points since September), while BlackBerry dropped a percentage point in the same period.

BlackBerry and iPhone were followed by Microsoft's Windows Mobile with 18 percent share, Palm with 6.1 percent share, and Google's Android with 5.2 percent share (up 2.7 percentage points).

The rapid rise of Android was before the January 2010 launch of Google's Nexus One smartphone.

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comScore released the data from the comScore MobiLens service, reporting key trends in the US mobile phone industry over the three-month period between September and December 2009.

The report also ranked the leading mobile original equipment manufacturers (OEMs) in the US according to their share of current mobile subscribers age 13 and older, as well as the most popular forms of content and activity accessed via mobile device.

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The report found Motorola to be the top mobile handset manufacturer with 23.5 percent market share.

A total of 234 million people age 13 and older in the US used mobile devices in December 2009. Device manufacturer Motorola was the top ranked OEM with 23.5 percent of US mobile devices.

LG ranked second with 21.9 percent share, followed by Samsung (21.2 percent share), Nokia (9.2 percent share) and RIM (7.0 percent share).

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In December 2009, 63.1 percent of US mobile subscribers used text messaging on their mobile device, up 2.1 percentage points from three months prior.

Browsers were used by 27.5 percent of US mobile subscribers (up 1.5 percentage points), while subscribers who played games made up 21.6 percent (up 0.2 percentage points).

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See also: Twitter - will Apple, Google dislodge BlackBerry?