Not an answer, but you should probably adjust by some sort of CA wage index rather than purely inflation, since a lot of things the government pays for have grown more expensive much faster than inflation (like salaries of sysadmins, and land). Looking at revenues as a percentage of state GDP would be one approximation (that would also bake in a correction for population growth).

I do think it's likely they haven't decreased greatly, though--- imo a bigger factor has been that where the money is spent has shifted greatly (less on education, more on cops and prisons, for example).