Last Friday, Facebook experienced a partial global blackout for about an hour during the prime news hours of 8 am to 9 am Pacific. The blackout caused a 3 percent drop in overall traffic to news websites, according to data from ChartBeat, a traffic analytics firm that partners with many news outlets.
From here. Also in that piece: “The drop was partially offset by 9 percent of readers going to directly to the homepages of their favorite news sites.”