The results of an attempt to answer the above has been reported recently in: How Readers Discover Content in Scholarly Publications by Tracy Gardner and Simon Inger (Published by Renew Training, a trading name of Simon Inger Consulting Ltd, March 2016). Read the full report at: http://www.simoningerconsulting.com/how_readers_discover.html. Findings are succinctly summarized in the Introduction. Ithaka's http://www.ithaka.org Roger C. Schonfeld comments in the 30 March 2016 Scholarly Kitchen post How Readers Discover Content in Scholarly Publications: http://scholarlykitchen.sspnet.org/2016/03/30/how-readers-discover-content-in-scholarly-pu.... Quotes are taken from Schonfeld's comments. Among his observations: ". . . the headline finding here is that the other means of discovery specified — everything from personal recommendations and social media to alerts and citations — collectively add up to drive more traffic than search." And he questions the finding: "The report finds a significant overall increase in the publisher website as a starting point for searches for journal articles on a specific subject . . . " What does make good sense to him: ". . . discovery patterns and practices vary across different sectors such as academic, corporate, and medical, different countries and levels of national income, and different fields and disciplines." Read both documents, citations and links are given above.