The 2015 CBMS Survey reveals that over the past decade, we have lost 2000 tenure lines while increasing the number of full-time contract faculty by over 3000.
Tenure line positions dropped from 17,256 to 15,270. Full-time non-tenure line faculty (including post-docs) increased from 5448 to 8579. Part-time faculty increased from 6536 to 7682.
Details at http://launchings.blogspot.com/2017/10/the-loss-of-tenure-positions-threats-to.html