Iowa Code § 519A.8: Participation.

All members of the association shall participate in its writings, expenses, servicing allowance, management fees and losses in the proportion that the net direct premiums of each member, excluding that portion of premiums attributable to the operation of the association, written during the preceding calendar year bears to the aggregate net direct premiums written in this state by all members of the association. Each member’s proportion shall be determined annually on the basis of the annual statements and other reports filed by the insurer with the commissioner.