About 49.3 million Americans are online during almost all their waking time: that is, one-fifth of U.S. adults say they go online “almost constantly,” and three-quarters at least once a day, according to a new survey from Pew Research Center. The 18-29 age group has the highest percentage of people online “almost constantly,” at 36%. The 30-49 age bracket is close behind, with 28% reporting that frequency of internet use.