[Higher Education] On Adjuncts to Tenured Professor Ratios

From the International Herald Tribune:

Three decades ago, adjuncts - both part-timers and full-timers not on a tenure track - represented only 43 percent of professors, according to the professors' association, which has studied data reported to the federal Education Department. Currently, the association says, they account for nearly 70 percent of professors at colleges and universities, both public and private.

Ah, the sweet smell of the long-term defunding of education.

Thanks, military-industrial complex! Political elites! Thanks, globalization!

While I'm interested in how this affects the student experience, I'm no student affairs professional, so my primary interest (at the moment) happens to be something not directly mentioned in the article:

Graduate students.

(And here is where it gets a little disjointed and rambly.)

Most college-level classes are taught by someone from the following list:

Tenured Faculty
Tenure-track faculty
professional faculty (support staff, deans, etc., who sometimes teach a single class)
specialized instructors (industry folks teaching a single class, for example)
Adjunct/Instructors (non-tenure track faculty)
graduate students

I'm guessing a bit, but I think as you move down the list, the cost to the university gets cheaper. (Though, to be honest, there are some graduate students who make more than adjuncts, depending on how you measure it.)

I'm not even going to touch the claim that quality changes linearly as you move down the list. I'm not sure it's true, but I have no way of - and no interest in - trying to quantify it on a large scale.

The point being that I want to know how graduate teaching assistants play into this. A few pieces of information:

Depending on the university, graduate students may or may not get a whole class to themselves to teach. They might just teach a section or a lab or recitation (or two, or three), for example. They might grade papers and proctor exams - or they might teach their own class and do everything. It varies.

I suspect GTAs who teach their own classes do not get graders, like many tenured faculty seem to. They're expected to do all the grading on their own. This keeps the cost per class down.

So. As the percentage of classes taught by adjuncts goes up, what happens to the share of the pie allocated to graduate students? Many graduate students use teaching as a way to pay for their education - to say nothing of the experience they get along the way.

Do adjuncts start getting TA graders? I doubt it. Do adjuncts encroach on traditionally GTA territory? Maybe, a bit, but again, I doubt it.

But the real question: To what extent are adjuncts and graduate students in competition for the same work? Is that changing?