Oregon Revised Statutes Insurance § 737.316

(1) All the employers in the group are members of an organization.

(2) The employers in the group constitute at least 50 percent of the employers in the organization, unless the number of covered workers in the group exceeds 500, in which case the employers in the group must constitute at least 25 percent of the employers in the organization.

(3) The grouping of employers is likely to substantially improve accident prevention, claims handling for the employers and reduce expenses.