Eski is quite right that state budgets have declined. However, school budgets have swelled, massively. I looked at this for Clemson on here a few years ago, so lets start there.
http://www.clemson.edu/administration/documents/budget.pdf
Looking at their 2007 budget, it went from $604mm to $989mm in 16-17, a 63.7% increase. During that time State appropriations went from $145mm to $109mm, or from 24.1% to 11%. In order to keep the same %, the state would have needed to increase the budget to $238mm. Instead, student fees went from $166 (27.5%) to $354mm (35.9%)
During that time Instruction costs went from $138 to $207. While Research went from $103mm to $152mm and Scholarships went from $82 to $105. Auxillary went from $79 to $154.
I couldn't find anything prior to that.
However, if we were to look at the cost per student for Clemson, we would find that it went from 18k to 23k. That means per student the Clemson annual budget was $35k. Now it is $43k, an increase of 22.8%. That's in a time the budget would increase 14% to keep up with inflation.
I wish I could see it longer-term than that.
Basically, budgets have gone up, funding sources have gone down, so tuition skyrockets.