Does Tenure affect quality of education?

I ran some numbers based on the 2014 IPEDS data and here is one interesting metric I discovered:

Top Universities with high percentage of Non-Tenure track faculty (These are folks who will never get tenure, they are not even on tenure track)

Vanderbilt: 63%
Columbia: 57%
Michigan: 56%
Duke 52%
UCLA: 48%

Top Universities with low percentage of Non-Tenure track faculty

MIT 1%
CalTech: 11%
GeorgiaTech: 12%
WashU, Berkeley: 17%
Princeton: 18%

Do you think this metric has any bearing on the quality of education a student receives at the University? Some say that tenure is an obsolete system and should be abolished. Others claim it protects faculty from political pressures. How do you think it affects how faulty approaches teaching?

Would love to understand what folks on CC think about this?

It depends - a school which uses non-tenure track instruction can do so for a number of reasons. Some schools use adjunct instruction in the arts, taking advantage of musicians and artists in nearby cities to teach students on a part time basis. That is great for students. Other schools may have shrunk the number of “lines” – full time regular tenure track faculty – and that will affect range and depth of course offerings. Still others may offer specialized positions where a professor may be on a “teaching only” track, without expectations in research and vice versa, research only, no teaching.

As a faculty family, I would say it takes research into the specific institution and departments to see what the numbers reflect.

The use of non-tenure track faculty is a tricky issue. The causality between its use and educational quality is probably going both ways.

On average, non-tenure track faculty is cheaper than tenure tack faculty from a university’s cost perspective. A university that is more willing to dilute its educational quality tend to has less problem using more non-tenure track (note that many universities will not want to dilute their educational quality). But this simple relation is often complexed by a few other things. For example, in some fields, say business and journalism, it is actually a good idea to use some non-tenure track faculty who have high-quality professional experiences (say a Fortune 500 CEO). Although I am not sure about this, but your ranking seems to suggest that, in contrast, in STEM this kind of benefit is probably lower. As a result, you have MIT, Cal Tech, etc. with a low %.