Moral hazard strategy and quality contract design in a two-echelon supply chain

Based on game theory and principal-agent theory, this paper focuses on how to control product quality and design quality contract in supply chain when moral hazard exists. We set up the supplier and buyer's expected profits function model, in which the supplier makes production process investment-level decision and decides on the product quality prevention level, whereas the buyer makes quality evaluation decision and decides on the product quality inspection level. The supplier with a moral hazard of reducing investment level may lack investment in the production process; thus, the buyer will pay the information rent to incentivize the supplier to improve the investment level. The buyer creates the moral hazard of exaggerating the product quality defective rate, who may overinvest in the inspection process. We use the optimal condition to solve supplier's first-best investment level, product quality prevention level, and buyer's first-best quality inspection level, internal penalty, and apportionment ratio of external failure cost. We also conduct a simulation test that shows the following: When the supplier improves its investment level, its product quality prevention level will increase, and the buyer's quality inspection level will decrease. With the improvement in the buyer's product quality inspection level, its internal penalty will increase, and the supplier's external failure cost will also increase while its expected profits will decrease. Hence, the buyer will design an incentive contract, the expected profits of which will increase, and the whole supply chain's joint expected profits function may become an inverse U shape. Finally, we develop a simulation example and propose suggestions for quality control strategy and contract design in the supply chain under the conditions of asymmetric information.