State laws based on a model law of the National Association of Insurance Commissioners (NAIC) that allow insurers to set rates independently; or adopt those rates developed by a rating bureau that must first be approved by the appropriate state regulator. Because state regulators believe that rate wars can be disastrous to the financial health of insurers, insurance companies are allowed to band together to set standard rates through rate making bureaus. Model rating laws also allow independent insurers to set their own rates, but prohibit the return of part of a premium to the insured other than as a dividend. Legislation developed from this model bill is called a prior approval law because the appropriate insurance commissioner must approve the rates involved. Other major types of rating laws are FILE-AND-USE RATING LAWS and OPEN COMPETITION LAWS.