Tero Kuittinen, a managing director at Frank N. Magid Associates, which found that the portion of 13- to 17-year-old U.S. social media users on Facebook slipped to 88 percent this year from 94 percent in 2013 and 95 percent in 2012. In the same period, Twitter and messaging applications rose in popularity among teens, though more people still use Facebook than any of its competitors. Walgreen, the drugstore chain that’s all over the Bay Area, reports quarterly earnings on Tuesday. Analysts estimate that net income will fall 13 percent to $607 million. Pharmacy sales for Walgreen and its main competitors, CVS and Rite Aid, are increasing as Medicaid coverage under the Affordable Care Act expands to more low-income people in 27 states.