Is there serious research showing the state of speech on campus? All I've seen is allegations and anecdotes and I fear an attempt to establish 'fact' via repet

Is there serious research showing the state of speech on campus? All I've seen is allegations and anecdotes and I fear an attempt to establish 'fact' via repetition, especially given the politicized nature of the issue (and this article and publication seem to reinforce the politicization problem). I find that only clouds issues - it's anti-information.