Google's Android operating system maintained its current domination of the U.S. smartphone market - accounting for 52 percent of units sold in the second quarter (Q2) of 2011.
Meanwhile, Apple's iPhone OS (iOS) experienced a slight quarterly gain - increasing to 29% in Q2 - as BlackBerry OS share plummeted to 11 percent.
As expected, Windows Phone 7, Windows Mobile and webOS managed to hold steady at less than five percent of the market each.
Interestingly enough, Motorola's overall mobile phone market share declined 3 percentage points, from 12% in Q2 2010 to 9% in Q2 2011.
Concurrently, the company's share of the smartphone market declined from 15% to 12%, as share of Android OS sales halved from 44% in Q2 of last year to 22% in Q2 of 2011.
However, NPD exec Ross Rubin believes Google's recent acquisition of Motorola Mobility could help the division get back on track.
"Much as it did in the feature phone market in the RAZR era, Motorola is experiencing increased competition from Samsung and LG in the smartphone market," he said. "Closer ties to the heart of Android can help inspire new paths to differentiation."
Rubin also noted that the acquisition effectively "shifts the balance of power" in the handset-patent conflict between Google and its operating system competitors.
"Android's momentum has made for a large pie that is attractive to Motorola's Android rivals - even if they must compete with their operating system developer," he added.