California Insurance Commissioner Dave Jones on Wednesday issued a notice to property/casualty insurers doing business in California advising them that so-called “price optimization” in rate making is unfairly discriminatory and violates the law.

Price optimization is the practice of setting rates based on an individual’s or class of individuals’ willingness to pay a higher premium relative to other individuals or classes. For example, if a price optimization analysis indicated that a consumer in one location was less likely to comparison shop than a consumer in another location, the insurer would charge the first consumer more for an identical policy—even if the two consumers had the exact same risk profile.

“It is illegal for an insurer to charge people different rates based on their sensitivity to price increases or the likelihood they will comparison shop,” Jones said in a statement. “Price optimization represents a fundamental threat to fairness in rating. As insurance commissioner, I remain committed to ensuring California maintains a healthy and vibrant insurance marketplace, while making sure consumers remain protected.”

The California Department of Insurance sent the notice to more than 750 property/casualty insurers instructing them to cease using price optimization and adjust their rates in California. They have been given six months to adjust rates and submit new filings to the department.