There was an article recently in the press about the odds of getting off a UC waitlist that may be of interest.
UC Berkeley accepted only 1% of students off the 2022 waitlist: 48 of the 4,650 students who opted in. UCLA’s rate was nearly as low, with 3.3% of waitlist applicants accepted, though the actual numbers were higher: 372 of 11,169 students who opted in. UC San Diego accepted 6.7% of waitlist applicants — 2,401 of 36,137 opt-ins.
Other campuses had higher percentages of waitlisted students admitted: UC Santa Cruz accepted 13%, UC Davis accepted 19%, UC Santa Barbara accepted 27%, and UC Riverside accepted 40%.
article (including a chart for all UCs 2020-22) is at UC admissions: What are the odds of getting off the wait list at UCLA, Berkeley and every campus?