In their monthly survey update on US phone usage, comScore reported that by the end of April 74.6 million people in the U.S. owned smartphones. In the same period a year ago only 48.1 million did. The percent of smartphone users out of total phone users has reached 32%.

The following data points can also be deduced:

• 2.1 million or 474k people/week became smartphone users during April.
• 62% of smartphones in use in the US are either Android or iOS. The sum a year ago was 37%.
• There are about 20 million iPhone users and 27 million Android users in the US today. A year ago there were 12 and 6 million respectively.
• RIM’s US user base peaked at 22 million in Sept 2010. It is now 19 million and dropping.
• Usage of Microsoft mobile operating systems in the US is in steady decline dropping from 7 to 5 million users in one year.
• During April 475,000 people abandoned their Blackberries.
• Android and iOS gained 3 million users in April. One million switched from other smartphones and 2 million switched from non-smartphones.

The following chart shows the evolution of installed base share of platforms among users of smartphones in the US.