Just one data point but I was born and raised in NorCal and in the 80’s when I graduated HS, UC Berkeley was considered the top public flagship in CA.
1980 data:
UCLA 74% acceptance rate, 67% yield
UCB 54% acceptance rate, 69% yield
**Source (for UCB) Academic Senate Berkeley Report “Freshman Admissions at Berkeley: A Policy for the 1990’s & Beyond” (1989)
Some other data points:
In 2000, UCLA had 20% more applicants (37,000 to 31,000) and in 2018, 27% more applicants (113,000 to 89,000).
IMO, UC Berkeley is more of an acquired taste with it’s liberal city, social activism, and East Bay culture which might not appeal to some applicants. Conversely, UCLA is in desirable West LA (Westwood) sandwiched between Beverly Hills and Brentwood/Santa Monica, has better year-round weather and very accessible to the beaches while still maintaining a world-class education.
I love the Berkeley area (even lived there for several years) but it’s not for everybody. I hate to say it but UCLA might have caught up to, or even surpassed, UCB as the state’s #1 public flagship (not withstanding individual majors, like Engineering for example).