Methodology:

The "current property tax valuation" is the assessed value for tax purposes. The "current property market value" is the estimated current sale price. To calculate current annual taxes we multiply the property tax valuation by the average San Diego County tax rate of 1.2%. To calculate "Fair Share" taxes, we multiply the current market value by the fair share tax rate of 0.46%.

Where do we get that? It's the rate that would produce the same total property tax receipts for the county if the average value of all parcels were equal to the 2022 average parcel value. That is, if valuations for property tax purposes were set at the market price, the tax rate could be cut by almost two thirds with no loss of revenue.