A basic model for co-ordinating a four-level supply chain of a product with a vendor, multiple buyers and tier-1 and tier-2 suppliers

This paper investigates the co-ordination of order quantities amongst the players in a four-level supply chain with a centralised decision process. The first level of the supply chain consists of multiple buyers, the second level of a vendor (manufacturer), the third level consists of multiple tier-1 suppliers, and the fourth level consists of multiple tier-2 suppliers. Each supplier supplies one or more items that are components of the product produced by the manufacturer. The model developed in this paper guarantees that the local costs for the players either remain the same as before co-ordination, or decrease as a result of co-ordination. A mathematical model is developed, with numerical examples presented and results discussed.