It's interesting that the enrollment has grown much faster than population growth (and I'd suspect, much faster than the population of the age 18-22 population, since there was a bulge in that age group in 1970). So what really may be happening is that the spending is spread thinner, as the "everybody should go to college" meme has spread.
True, although the spending is down from 1985-1990 levels even without the per-student calculation. It doesn't seem to be for explicitly partisan reasons either, since the UC system was well-funded under Deukmejian (a Republican) and then had its funding cut under Wilson (also a Republican).
Interestingly, most of the faster-than-population enrollment surge is in the past 5 years. If enrollments had grown from 1970 to 2000 in line with the results of the 1970 census versus the 2000 census, they would've been 124,000 in 2000, which is not that much lower than the actual 141,000 (that's only a 15% growth in enrollment rates over 30 years).
This could additionally be influenced by any number of schemes which increase both the size and number of college loans, e.g., government-guaranteed loans resulting in higher willingness to lend than might otherwise occur. Such subsidies (be they real or perceived) would tend to result in higher tuition rates for private schools, and lower subsidy amounts for state schools.
