Daily Digit is the story behind the numbers that make our world work. Today, we’re looking at something that could be a sign that Facebook is in for more trouble: Teens are turning away from the social network. Ninety-five percent of teens have access to a smartphone, and 45 percent say they are online “almost constantly.” However, according to a recent survey, Facebook's youngest users (ages 13 to 17) are logging on at a far lower rate than their counterparts in almost every other age group. In fact, the only age group that uses Facebook less frequently are people age 65 and older. But that doesn't mean teens are shying away from social media altogether; instead, they're opting for other platforms — such as YouTube, Snapchat, and Instagram.