An analysis of data from Georgetown University’s Free Speech Project by the project’s director, Sanford Ungar, published on Medium. FSP’s data covers all types of free speech incidents, ranging from professors’ dismissals to university administrators admonishing students over speech. At the time of Ungar’s writing, FSP had cataloged roughly 60 such incidents on college campuses between 2016 and today.

Acadia University professor Jeffrey Sachs’s data on professors being fired for political speech, as published in a piece for the left-libertarian Niskanen Center. This shows “45 cases from 2015 to 2017 where a faculty member was fired, resigned, or demoted/denied promotion due to speech deemed by critics as political,” fewer than a third of whom (13 out of 45) were conservative.

Data on speaker disinvitations from the Foundation for Individual Rights in Education (FIRE) which shows 20 to 42 such disinvitations per year between 2011 and 2017.