This industry comprises establishments primarily engaged in the merchant wholesale distribution of a general line of groceries and sponsoring (or affiliated with sponsors of) voluntary organization of food retailers which distributes a general line of groceries to these voluntary groups. These also include any voluntary group grocery merchant wholesalers commonly engaged in joint advertising or other sales promotions under a group name or identification. Merchant wholesale establishments sponsoring such voluntary groups are included here regardless of the portion of their sales made to the retail organization's members.