Still at Android Developer Conference, where Don Kellogg, director of telecom research for Nielsen. In his day job, he analyzes the information Nielsen gathers from its pool of research subjects, who have their bills scraped, answer surveys, and even install monitoring applications on their phones which anonymously record their activities and usage statistics.

"I get to play with all our cool research and share it with you," said Kellogg. His talk was a flurry of statistics and information on smartphone users, so we'll attempt to relay the interesting figures herein.

"The thing that's exciting about Android and the mobile ecosystem in general, is that one of the core things you have to compete on is how friendly are you to developers," said Kellogg.

Kellogg said the average smart phone user uses 38 applications in a given month. He also stated that, currently, 44% of Americans have smart phones. "The growth of smart phones is not a hockey stick graph. We're going to hit the 50% penetration rate somewhere between February and March of next year. Given the Apple launch of the iPhone 4GS, it may be closer to January," said Kellogg.

Kellogg went on to show off a day in the life of an average smart phone user. For that user, phone calls account for less than 3% of the overall usage time. 94.1% of the time, the device was not active. 5.9% of the time it is active. Users average 1:25:14 hours of use per day.

What are those users doing during that time? 40% of that usage time is spent on Facebook, either on the Web or on the native Facebook app. 28% of that time is spent gaming. Messaging takes up 8%, and Internet usage was 12%. Beyond that, 1% of time was spent on email, 7% on preloaded applications, and only 1% on third party applications.

The growth of smart phone usage and of mobile Internet usage has been a major trend for Kellogg to follow. He said that in Q2 of 2010, there were only 34 million mobile Internet users in the U.S. In Q2 2011, that number grew to 52 million users. In Q2 2010, only 27 million smart phone users downloaded applications, while in Q2 2011, that number was up to 44 million users. Perhaps the largest growth was in streaming media applications. I Q2 2010, 15 million users used streaming media on their smart phone. In Q2 2011, that number was up to 26 million users. Kellogg gave a nod to Pandora for this increase.

In the area of demographics, Kellogg showed that, by manufacturer, Motorola device users tended to be the most affluent and wealthy. He showed over 34% of Motorola Android owners were making over $100k per year. He added that Motrola devices are popular on Verizon's network, and that this skews those numbers higher, as Verizon customers tend to be wealthier than other mobile carrier users.

Perhaps the most interesting bit of information Kellogg intimated was the relative popularity of the various Android devices. He showed the HTC Evo 4G was the single most popular Android handset, both overall, and within the last quarter. The Motorola Droid X came in second overall, and the LG Optimus S placed third overall.

"You need to make sure you test on the Evo," aid Kellogg. "The other thing I'd point out is there are a lot of large format screen devices here. The Evo, the Droid X, and the Samsung Charge. Make sure if you're developing applications, you develop for a larger screen size."

He also showed that reviews make a big difference to users. "You cannot release an app that is not fully baked because people use reviews quite a bit. Make sure when you release your app that it's ready. 61% of folks say reviews are extremely or very important. It's OK to iterate and improve, but make sure it's ready," said Kellogg.

Then came the bad news. Unfortunately, the top ten applications in the Android app store account for 34% of all time spent with third party applications on Android devices. The next ten most popular apps equate 8%, the next ten another 8% and the final ten apps in the top 50 make up 2% of the overall app usage. The whole rest of the store eats up only 47% of all time.

Fortunately, the story is much the same on iOS: the top ten applications make up 45% of the overall app usage on that platform.

Kellogg, finally, explained how applications get upgraded. Most users said they upgraded from a free version to a paid for version because they wanted additional functionality. The least successful upgrade trick, however, was using a timed trial. When the time runs out on the trial version, under 25% of users upgraded. "Don't make your free app or your trial app too good. You don't want to make it expire, but you don't want to make it good enough so people wont buy the full version."

Kellogg blogs at Nielsen's site, and offers interesting info from time to time. His slides will be on the Android Developer Conference site shortly.