Fifty-five percent of people surveyed by Nielsen in May reported buying a smartphone instead of a standard cell phone, up from 34 percent a year ago.
The data is the latest indication that a sizable chunk of Americans are using their phones to access the Web, download apps and exchange media such as photos and video. Thirty-eight percent of mobile-phone owners now own a smartphone, according to the latest survey.
Android remains the most popular smartphone platform with 38 percent of the market, followed by Apple at 27 percent and RIM's BlackBerry with 21 percent.
Android also leads Apple among people who purchased smartphones in the past three months, at 27 percent and 17 percent respectively.