Mo. Rev. Stat. § 376.874

Medicare supplement policies shall return to policyholders benefits which are reasonable in relation to the premium charged. The director shall issue reasonable regulations to establish minimum standards for loss ratios of Medicare supplement policies on the basis of incurred claims experience, or incurred health care expenses where coverage is provided by a health maintenance organization on a service rather than reimbursement basis, and earned premiums in accordance with accepted actuarial principles and practices.