Supply chains can be complex, involving many participants, intermediaries, and service providers to facilitate the movement of goods and services from sourcing to consumption. Thus, the channel functions and activities of wholesaler-distributors can be, and often are, performed by other supply chain participants. For example, manufacturers’ sales branches are captive wholesaling operations that are owned and operated by manufacturers. Many manufacturers also have sales offices to perform certain selling and marketing functions. These locations do not take physical possession of inventory and may work with independent wholesaler-distributors. customers, particularly larger multi-establishment retail firms, often perform the functions of wholesale distribution. These represent the vertical integration mode of governing the channel, either forward integration by the manufacturer or backward integration by the end customer in the B2B sector. Unfortunately, limited comparable data exist about the overall magnitude or importance of these activities.