How Much Do UC Essays Matter?

I’ve heard through the grapevine at my school that the UCs are mainly focused on grades and test scores, and that some of the “lower tier” ones (UCSB, UCSC, UCM, UCI, maybe even UCSD and UCD) do not even read the essays. But since they’ve just changed the UC prompts to the personal insight questions, does that mean that all of them are more likely to read the essays? Does anyone have any data about the weight UCs put into grades, ECs, test scores, essays, etc?

Look at the common dataset for each school and it spells out what they consider Highly important, Considered and Not considered. For example UCR, application essays are considered Highly Important. Section C7

http://ir.ucr.edu/cds/15-16/CDS-PartC.xls

Thank you!