Cal. Rev. & Tax. Code § 38202

During December, 1978, and December of each subsequent year, after public hearings, the board shall adjust the yield tax rate to the nearest one-tenth of 1 percent in the same proportion that the average rate of general property taxation in the rate adjustment counties in the current tax year differs from the average rate of general property taxation in the rate adjustment counties in the preceding tax year. The board shall compute the average rate of general property taxation in the rate adjustment counties by (a) adding the county, city, school district, and other general taxes, but not the special taxes on intangibles, aircraft, or any other property, which is subject to a uniform statewide tax rate, nor special assessments, and (b) dividing the amount obtained by the total assessed valuation in the rate adjustment counties, exclusive of the homeowners’ and business inventory exemptions, as shown by the county tax rolls for the same year.

“Total assessed valuation,” as used in this section, does not include the assessment of property which is subject to a uniform statewide tax rate.

“Special assessment” as used in this section, means any amount levied solely against land or land and improvements.

When calculating the yield tax rate for the 1981–82 fiscal year, the 1980–81 average rate of general property taxation should first be divided by four.