Cal. Const. art. XIII, § 18

The Board shall measure county assessment levels annually and shall bring those levels into conformity by adjusting entire secured local assessment rolls. In the event a property tax is levied by the State, however, the effects of unequalized local assessment levels, to the extent any remain after such adjustments, shall be corrected for purposes of distributing this tax by equalizing the assessment levels of locally and state-assessed properties and varying the rate of the state tax inversely with the counties’ respective assessment levels.