(1) All rates shall be made in accordance with this section and all of the following:

  (a) Due consideration shall be given to past and prospective loss experience within and outside this state; to catastrophe hazards; to a reasonable margin for underwriting profit and contingencies; to dividends, savings, or unabsorbed premium deposits allowed or returned by insurers to their policyholders, members, or subscribers; to past and prospective expenses, both countrywide and those specially applicable to this state; to underwriting practice, judgment, and to all other relevant factors within and outside this state. For worker’s compensation insurance, in determining the reasonableness of the margin for underwriting profit and contingencies, consideration shall be given to all after-tax investment profit or loss from unearned premium and loss reserves attributable to worker’s compensation insurance, as well as the factors used to determine the amount of reserves. For all other kinds of insurance to which this chapter applies, all factors to which due consideration is given under this subdivision shall be treated in a manner consistent with the laws of this state that existed on December 28, 1981.

  (b) 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 the 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.

  (c) Risks may be grouped by classifications for the establishment of rates and minimum premiums. Classification rates may be modified to produce rates for individual risks in accordance with rating plans that measure variations in hazards, expense provisions, or both. The rating plans may measure any differences among risks that may have a probable effect upon losses or expenses as provided for in subdivision (a).

  (d) Rates shall not be excessive, inadequate, or unfairly discriminatory. A rate shall not be held to be excessive unless the rate is unreasonably high for the insurance coverage provided and a reasonable degree of competition does not exist with respect to the classification, kind, or type of risks to which the rate is applicable. Except as otherwise provided in this subdivision, a rate shall not be held to be inadequate unless the rate is unreasonably low for the insurance coverage provided and the continued use of the rate endangers the solvency of the insurer; or unless the rate is unreasonably low for the insurance coverage provided and the use of the rate has or will have the effect of destroying competition among insurers, creating a monopoly, or causing a kind of insurance to be unavailable to a significant number of applicants who are in good faith entitled to procure the insurance through ordinary methods. For commercial liability insurance a rate shall not be held to be inadequate unless the rate, after consideration of investment income and marketing programs and underwriting programs, is unreasonably low for the insurance coverage provided and is insufficient to sustain projected losses and expenses; or unless the rate is unreasonably low for the insurance coverage provided and the use of the rate has or will have the effect of destroying competition among insurers, creating a monopoly, or causing a kind of insurance to be unavailable to a significant number of applicants who are in good faith entitled to procure the insurance through ordinary methods. As used in this subdivision, “commercial liability insurance” means insurance that provides indemnification for commercial, industrial, professional, or business liabilities. For worker’s compensation insurance provided by an insurer that is controlled by a nonprofit health care corporation formed pursuant to the nonprofit health care corporation reform act, Act No. 350 of the Public Acts of 1980, being section 550.1101 to 550.1704 of the Michigan Compiled Laws, a rate shall not be held to be inadequate unless the rate is unreasonably low for the insurance coverage provided. A rate for a coverage is unfairly discriminatory in relation to another rate for the same coverage, if the differential between the rates is not reasonably justified by differences in losses, expenses, or both, or by differences in the uncertainty of loss for the individuals or risks to which the rates apply. A reasonable justification shall be supported by a reasonable classification system; by sound actuarial principles when applicable; and by actual and credible loss and expense statistics or, in the case of new coverages and classifications, by reasonably anticipated loss and expense experience. A rate is not unfairly discriminatory because the rate reflects differences in expenses for individuals or risks with similar anticipated losses, or because the rate reflects differences in losses for individuals or risks with similar expenses. Rates are not unfairly discriminatory if they are averaged broadly among persons insured on a group, franchise, blanket policy, or similar basis.

  (2) Except to the extent necessary to meet the provisions of subsection (1)(d), uniformity among insurers in any matters within the scope of this section is neither required nor prohibited.