Every health insurer that issues, sells, renews, or offers health insurance policies for health care coverage in this state, including a grandfathered health plan, but not including specialized health insurance policies, shall provide an annual rebate to each insured under such coverage, on a pro rata basis, if the ratio of the amount of premium revenue expended by the health insurer on the costs for reimbursement for clinical services provided to insureds under such coverage and for activities that improve health care quality to the total amount of premium revenue.