Teens who have cell phones are much more likely than the rest of their peers to use the internet daily, listen to the radio, and read newspapers and magazines, MediaWeek reports, pointing to a study by WPP Group's MindShare Online Research. Cell phone ownership among U.S. teens 13-17 increased 43 percent in the past year, with teen girls (61 percent) more likely to carry them than teen boys (46 percent). And daily cell phone usage has more than doubled in the past year, again with teen girls leading the way 41 percent to 27 percent. Those who carry phones are heavy users: 83 percent use them daily; 64 percent use them at least several times a day.