Here is a page from UC Merced:
https://cie.ucmerced.edu/undergraduate-applicants-admits-enrollments
On the “Table: Single Year by Major” and “Table: Annual by Characteristic”, it shows, applicants, admits, SIR_Y, and enrollments. SIR_Y is the number or percentage of admits who make enrollment deposits; the percentage is conventionally called yield (SIR = “statement of intent to register”).
For fall 2022 entering students, note that SIR_Y → enrollments is only 72% for regular frosh and lower for other groups of applicants / admits (“referral” refers to UC ELC or top 9% statewide applicants referred to UC Merced after being shut out of all UC campuses they explicitly applied to). This means that “summer melt” at UC Merced is >28%. Presumably, this means that many SIR_Y students got off a waitlist, decided to switch to a community college, or decided not to attend college at all.
How large is “summer melt” at other colleges?