California Code, Public Utilities Code - PUC § 28745.8

The establishment of election districts shall be made on the basis of the population in the district as shown or estimated from the most recent of any of the following:  the last federal decennial census;  any census of a county, taken as provided in Section 26203 of the Government Code, or census of a city, taken as provided in Chapter 17 (commencing with Section 40200), Part 2, Division 3, Title 4 of the Government Code;  any census or population estimate of a city or of a city and county, taken or made as provided in Section 2107.1 or 2107.2 of the Streets and Highways Code;  or population estimates contained in any official document prepared by the Department of Finance and issued to the public.