Google's (NASDAQ:GOOG) Android operating system completed 2011 with 47 percent of ad impressions across smartphones, with Apple (NASDAQ:AAPL) also finishing the year strong at 33 percent of impressions, thanks to its iPhone.
The statistics came by way of an annual report from mobile ad firm Millennial Media, which is going public this year as the largest independent network, competing with Google, Apple (NASDAQ:AAPL) and other smaller rivals.
Android impressions grew a whopping 504 percent year-over-year, with 13 of the top 20 phones on Millennial's platform running on that OS.
In a sign of just how far the open-source platform has come under the aegis of Google, iOS commanded 41 percent of mobile ad impressions in 2010, compared with just 30 percent for Android.
However, Android was on track to finish the year with over 50 percent impression share, with iOS under 30 percent. That was the case until Apple's iPhone 4S launched in October and propelled Apple to 37 million in iPhone sales for the fourth quarter. iPhone 4S, no doubt, helped iPhone rise to 33 percent for 2011.
Apple was also the top OEM on Millennial's network for the second year in a row, netting 26 percent impression share, thanks to its iPhones and iPads.
Samsung, which just announced it has sold more than 20 million Galaxy S II smartphones, was No. 2 with 16.8 percent total impression share, spanning Android handsets and tablets.
Apple's iPhone took the No. 1 spot for impression share for a single phone, with 15 percent. Research in Motion's (NASDAQ:RIMM) Blackberry Curve was second on this list with less than 6 percent share.
Some of the more popular Droids on Millennial included the Motorola Droid, LG Optimus, HTC Evo, Samsung Galaxy S and the Motorola Droid X.
Topping tablet impression share on Millennial was, to no one's surprise, the iPad. Samsung again followed Apple, with roughly more than half the impression share of the iPad.
Amazon's (NASDAQ:AMZN) Kindle Fire also came on strong soon after launch, growing at an average daily rate of 19 percent impression share, nudging past even the growth of the first iPad at its launch.