^ Figures I have show Michigan with about 107,000 new HS grads in 2015, and California with 448,000. I think you’re using older data; Michigan’s school-age population has been declining, while California’s is growing.
I take your point that UC Berkeley enrolls a much smaller fraction of the state’s HS grads than Michigan does. I’m not sure which way that cuts, however. Inter alia, it means UC Berkeley has a much larger pool of black and Hispanic HS grads from which to recruit qualified applicants.
And despite drawing from a much smaller in-state pool, Michigan’s entering class stats are virtually indistinguishable from UC Berkeley’s
Michigan middle 50% (2015-16):
SAT CR 630-730
SAT M 660-770
ACT 29-33
UC Berkeley middle 50% (2015-16):
SAT CR 610-730
SAT M 640-770
ACT 29-34
It could be, however, that Michigan’s large OOS cohort pulls up its standardized test medians.