New study (US only) by the Knight Foundation: https://medium.com/mobile-first-news-how-people-use-smartphones-to , summarized here: http://www.theatlantic.com/technology/archive/2016/05/people-love-wikipedia/...

"People spent more time on Wikipedia’s mobile site than any other news or information site in Knight’s analysis, about 13 minutes per month for the average visitor. CNN wasn’t too far behind, at 9 minutes 45 seconds per month. BuzzFeed clocked in third at 9 minutes 21 seconds per month. (BuzzFeed, however, slays both CNN and Wikipedia in time spent with the sites’ apps, compared with mobile websites. BuzzFeed users devote more than 2 hours per month to its apps, compared with about 46 minutes among CNN app users and 31 minutes among Wikipedia app loyalists.)

Another way to look at Wikipedia’s influence: Wikipedia reaches almost one-third of the total mobile population each month, according to Knight’s analysis, which used data from the audience-tracking firm Nielsen."