Procurement in Supply Chains When the End-Product Exhibits the 'Weakest Link' Property

We consider a supply chain with one manufacturer who assembles an end-product using multiple outsourced parts. The end-product exhibits the “weakest-link” property, such that if any of its component parts fails, the end-product fails. The supplier of each component part can improve the (uncertain) quality of her parts by exerting costly effort that is unobservable to the manufacturer and is non-contractible. We analyze three possible contractual agreements between the manufacturer and suppliers: Acceptable Quality Level (AQL), Quality–Based Incentive Pricing (Q–Pricing) and Group Warranty. Under AQL, the manufacturer inspects all incoming parts, but establishes different quality thresholds and pays the suppliers different amounts for achieving the different thresholds. Under Q-Pricing, the manufacturer also inspects all incoming parts but pays each supplier a constant amount for each good part. Under Group Warranty there is no testing of the individual parts; instead all suppliers are responsible for any failed end-product. We compare the efficiency of these three contractual arrangements as a function of the exogenous variables.