UCSB Fall 2018 freshman acceptance rates by residency:
29.7% CA residents
47.7% US out-of-state
34.3% International
UCLA provides a detailed breakdown of student stats by residency. At UCLA, the OOS and International admits actually have better stats than the CA admits. I suspect that this is probably true at UCSB as well, but I don’t think UCSB provides the numbers. If so, this would be one reason for the higher OOS/International acceptance rates.
The OOS/International admits have significantly lower yields than CA residents. In other words, they are much less likely to attend UCSB if accepted. This doesn’t seem surprising, given that (1) the OOS/International students typically live much farther away, and (2) they don’t get any financial aid. So this is another reason that the OOS/international acceptance rates are higher.