Homeowners who have homes drop in value can file appeal for reassessment. I remember in 1990, I got a 20% decrease in my assessed value thus resulting in a 20% decrease in property taxes. The re-assessment is no automatic. Homeowners have to apply to get it. The only problem is the base on which future increases are calculated is not permanent adjusted down. By law, assessments can increase 2% per year compounded annually.
I expect a drop in tax revenue in the next few years. Not only will individual homeowners appeal but so will owners of large hotels and business buildings. That will mean many millions in decreased tax revenue. In the 1990 downturn, SF lost millions from the TransAmerica building alone.
Reporters in the media should periodically ask the County Assessor about the number of appeals. That would clearly indicate a downward trend.