379.318.  Rates, how made. — Rates shall be made in accordance with the provisions of this section:

  (1)  Due consideration shall be given to past and prospective loss experience within and outside this state, to conflagration and catastrophe hazards, if any, to a reasonable margin for underwriting profit and contingencies, to dividends or savings allowed or returned by insurers to their policyholders or members, to past and prospective expenses both countrywide and those specially applicable to this state, to all other relevant factors, including trend factors, within and outside this state, and in the case of fire insurance rates, to the underwriting experience of the fire insurance business during a period of not less than the most recent five-year period for which such experience is available and relevant.

  (2)  Risks may be grouped by classifications, by rating schedules or by any other reasonable methods, for the establishment of rates and minimum premiums.  Classification rates may be modified to produce rates for individual risks in accordance with rating plans which establish standards for measuring variations in hazards or expense provisions, or both.  Such standards may measure any differences among risks that can be demonstrated to have a probable effect upon losses or expenses.

  (3)  The systems of expense provisions included in the rates for use by any insurer or group of insurers may differ from those of other insurers or groups of insurers to reflect the requirements of the operating methods of any such insurer or group with respect to any kind of insurance, or with respect to any subdivision or combination thereof for which subdivision or combination separate expense provisions are applicable and shall accurately reflect the expenses of insurers or groups of insurers.

  (4)  Rates shall not be excessive, inadequate or unfairly discriminatory. No rate shall be held to be excessive unless such rate is unreasonably high for the insurance coverage provided and a reasonable degree of competition does not exist in the area with respect to the classification to which such rate is applicable.  No rate shall be held to be inadequate unless such rate is unreasonably low for the insurance coverage provided and is insufficient to sustain projected losses and expenses; or unless such rate is unreasonably low for the insurance coverage provided and the use of such rate has, or if continued, will have, the effect of destroying competition or creating a monopoly.  Unfair discrimination shall be defined to include, but shall not be limited to, the use of rates which unfairly discriminate between risks in the application of like charges or credits or the use of rates which unfairly discriminate between risks having essentially the same hazard and having substantially the same degree of protection against fire and allied lines.

  (5)  Uniformity among insurers in any matters within the scope of this section is neither required nor prohibited.