Which of the following describes the least formal power structure among marketing channel members?

The least formal power structure among marketing channel members is best described by an independent marketing channel. In this structure, each channel member operates independently, without a formal agreement or centralized control governing their relationships. This independence means that decisions are made individually by each participant, leading to a more flexible and less structured environment.

In contrast, a contractual vertical marketing system involves formal agreements between independent firms that allow them to work together while maintaining their independent status. This arrangement usually has specified roles and expectations, creating a more structured relationship. Similarly, a corporate vertical marketing system is characterized by a single company owning multiple levels of the distribution channel, thereby exerting significant control and formalizing relationships between those levels. An administered vertical marketing system, while still less formal than a corporate arrangement, relies on the dominance of one channel member to coordinate and influence the actions of others.

The independent marketing channel stands out as the least formal arrangement because it lacks the regulatory framework, contractual obligations, and centralized authority typical of the other options, allowing members to engage in transactions as they see fit, based on market conditions and their own strategic interests.