S.C. Code Ann. § 38-77-130: Group automobile insurance; rate.

An automobile insurer may negotiate and contract for the sale of automobile insurance with any bona fide group of twenty or more persons who are employed by a common employer or who have been members for six months or more of a fraternal order, labor union, or employment association. The insurer may negotiate, enter a contractual relationship, and service the contract solely and directly with the bona fide representative of the group. An insurance contract sold on the basis of a group plan or contract shall have a rate not less than five percent less than the individual rate for which the insurer markets a substantially similar policy.