By statute (RCW 51.32.073 (www.leg.wa.gov)) the Supplemental Pension Rate is rated on a pay-as-you-go basis and so it is not experience rated.

The Supplemental Pension Fund premiums cover the annual cost of living increases in pension and time-loss benefits that are paid during the rating year. The same rate is paid by all risk classifications and is also paid by self-insured employers and workers.

Half the premiums are paid by the workers and half are paid by the employers.