A new tool from the eCampusOntario Open Library measures student savings from open educational resources (OER) usage. Impact, as it's called, recently calculated that students have saved some $4.5 million (Canadian) in "mandatory textbook fees" from Ontario instructors who use OER to replace at least one of their assigned resources. That total represented input from almost 100 educators teaching 41,150 learners attending 626 course sections in 34 institutions.
https://campustechnology.com/articles/2019/07/09/ontario-schools-tally-oer-savings-with-new-tool.aspx?admgarea=news