According to an October 23, 2018, USA Today article by Charisse Jones, the pay gap which women suffer below men in the United States is smallest in California. However, this disparity has women being paid 89 cents for every dollar brought home by a man in California, which is still unequal. Fortunately, California law makes it unlawful for an employer to engage in unfair practices of paying an employee of the opposite sex (or another race or ethnicity) lower wage rates for substantially similar work under similar working conditions.
A wage differential is allowed only if an employer demonstrates that the pay difference is based on: (A) a seniority system; (B) a merit system; (C) a system that measures earnings by quantity or quality of productions; or (D) a bona fide factor such as education, training, or experience. In other words, the burden is on the employer to prove a legitimate reason for any pay disparity between men and women which is not based on sex. This can be a difficult burden for employers to meet.
(See Link(s): Labor Code Section 1197.5)