People spend about one-third of their online time each week on Facebook, a trend that gives retailers and other businesses a chance to use social media to reach their target market, according to a new study by research firm Morpace. Consumers spend an average of 7.3 hours each week on Facebook, and 22.4 hours on the Internet overall. Those ages 18-34 spend 8.5 hours a week on Facebook. People who have an income of more than $100,000 per year spend even more time on Facebook at 9 hours per week.