According to Comscore data of U.S. users, Facebook saw its share of visitors between the ages of 35-54 drop 3.6% to 35.4%, while the share of visitors under 18 (up 1.2 to 11.1% and age 55 and older (up 1.9 to 13.2%) made the biggest gains. Twitter saw a 9.4% gain in the share of 18-34 year olds visiting the site while those under 18 use fell 8 points to 9.5%. Here's the chart:
