CA Gov't Code Section 65063.1

The number of members of the board to which each county is entitled shall be determined as follows:

(a)

Each county having, within the district, a population of 350,000 or less shall have two (2) members of the regional planning board, one (1) appointed by the board of supervisors and one (1) appointed by the city selection committee.

(b)

Each county having, within the district, a population of more than 350,000 and not more than 600,000 shall have four (4) members of the regional planning board. Two members shall be appointed by the board of supervisors and two (2) members shall be appointed by the city selection committee.

(c)

Each county having, within the district, a population of more than 600,000 shall have six (6) members of the regional planning board. Three (3) members shall be appointed by the board of supervisors and three (3) members shall be appointed by the city selection committee. The population figures as used herein shall be determined by the latest official census.