Just a quick observation. Graduate school enrollment in public universities has been dropping since the early 90’s, while enrollment in private (not-profit) universities has been steadily rising.
It is hard not to imaging a steal effect going on there, where the privates get students who might have otherwise enrolled in the publics. But I’m certain the causes and the effects are much more complicated than simple competition between schools.
Some responsible forces off the top of my head range from reduced state support of the publics, narrowing tuition rates between the two, to endowment growth at the privates to relative successes in growing research infrastructure and the graduate enrollment that research will drive.
Of course, ultimately these numbers reflect where students choose to attend. This just relfects the evolving marketplace for the Master’s degree. If the students hold the cards–in the end, nobody can force a student to attend someplace they don’t wish to attend–what the graduate students seem to be saying is that the graduate school value proposition at private universities and colleges exceeds that of the public institutions.
If you add the private for-profit graduate school enrollment to that of the private non-profits, you get the inset result: Graduate school enrollment is higher now in private than in public colleges and universities. The inflection point actually occurred in 2008 and it is really difficult to see how this trend will ever be reversed.