A rating organization or any insurer making its own rates may, with the approval of the commissioner, from time to time, alter, supplement, or amend its rating plans, or any part thereof, by filing with the department copies of such alterations, supplements, or amendments, together with a statement of the reason, or reasons, for such alteration, supplement, or amendment. If such alteration, supplement, or amendment shall have the effect of increasing or decreasing rates, the commissioner shall determine whether the rates as altered thereby are reasonable, adequate, and not unfairly discriminatory. If the commissioner shall determine that the rates as so altered are not unreasonably high, or inadequate or unfairly discriminatory, he shall make an order approving them. If he shall find that the rates as altered are unreasonable, inadequate, or unfairly discriminatory, he shall issue an order disapproving such alteration, supplement, or amendment. Notwithstanding the foregoing, but subject to the provisions of Section 27-13-68, to the extent not inconsistent with this section, when a filing of adjustments of rates for existing classifications of risks does not involve a change in the relationship between such rates and the expense portion thereof, or does not involve a change of the element of expenses which are paid as a percentage of premiums or does not involve a change in rate relativities among such classifications on any basis other than loss experience, such filing shall become effective upon the date, or dates, specified in the filing and shall be deemed to meet the requirements of this article. The foregoing provisions shall not apply to workmen's compensation and employers' liability insurance.