California employers can pay employees unequal wages for doing substantially similar work for reasons that: 1) have nothing to do with sex, race, or ethnicity; 2) are job-related; and 3) are consistent with a business necessity. Examples include:
merit;
productivity;
seniority; and
other bona fide factors such as education, training, and experience.
Example: Tom has been working the same factory job for 20 years. Tina is hired for the same job, having no prior experience. Even though Tom and Tina are doing identical work, it is reasonable for Tom to receive higher wages than his new female colleague because Tom has two decades more experience.
In short, wage disparities between workers who do similar jobs are legal as long they are reasonably based on legitimate factors and not on conscious or unconscious bias, prejudice, or discrimination.