When we discovered that the average cost of tuition at four-year higher education institutions was largely pacing the growth of total federal government spending in the United States, that was a very surprising result. The reason why that's surprising is because of how most universities are funded.
According to Table 5 of the Digest of Education Statistics 2009, as of the 2007-08 school year, there were 2,675 Title IV degree-granting institutions (aka "colleges and universities") in the U.S. Of these, 653 were public institutions (mainly state universities) and the remaining 2,022 were private institutions.
But it is the size of the institutions that matters, not their numbers. In the U.S., 92 of the top 100 universities by enrollment are public, state-supported universities and 77% of all college students attend state-supported institutions. As a result, we would then expect the average tuition figures for four-year public institutions to closely follow state-level government spending and not the federal government's total level spending from year-to-year.