关键词: 供应中断, 战略库存, 应对策略, 横向联盟

Abstract: With the continuous upgrading of economic globalization and integration, supply chain networks expand further. Under the principle of prioritizing efficiency, every link is efficiently interfaced and tightly interconnected, which increases the dependency among network members. However, this also makes supply chain structure more complex and fragile, and more susceptible to the threat of disruption by various emergencies, such as earthquakes, political frictions, and strikes. If an upstream firm is forced to disrupt the supply due to these emergencies, this will not only affect its own interests but also bring serious consequences to midstream and downstream firms. Based on business practices and qualitative researches, some scholars have argued that building redundancy into the supply chain can effectively prevent, avoid or mitigate the risk of supply disruption, and reduce the resulting losses. Major strategies for building redundancy include multi-sourcing, contingency option, back-up supply, flexible operation and joint strategic inventory. Through literature review, it can be found that the first four coping strategies have yielded a great number of research results, but few scholars combine joint strategic inventory and supply disruption to conduct quantitative research on models. Joint strategic inventory strategy refers to the firm cooperating with other firms to jointly bear inventory costs, which can be divided into vertical joint and horizontal joint form. Horizontal joint form refers to the firm reserving strategic inventory jointly with other peer firms that purchase similar products or components. This strategy can not only reduce inventory redundancy and costs of individual firm, but also achieve dynamic complementarity of inventory by seeking help from other firms in the event of upstream supply disruption, thus effectively reducing the losses caused by supply disruption.
In view of this, this paper considers the scenario in which the retailer engages in the horizontal alliance with other peer firms sourcing similar products to jointly reserve strategic inventory to resist the risk of disruption from upstream suppliers. A three-stage game-theoretic model is constructed to decide retailer's strategic inventory reserve, product procurement, and emergency dispatch, and then the optimal equilibrium solution of the model is obtained using the backward induction method, the Lagrange multiplier method, and the KKT condition. On this basis, through parameter sensitivity analysis, the effects of procurement costs, reliability coefficient, supply proportion, and market shrinkage rate on retailer's strategic inventory level, product procurement volumes, emergency dispatch volumes, and expected profits are explored and studied.
The results of the study show that:(1)As the unit procurement costs of products increase, retailer's reserve volumes of the strategic inventory, product procurement volumes, emergency dispatch volumes, and expected profits all decline. (2)If the redundancy of the horizontal joint strategic inventory is higher, as the manufacturer's reliability increases, retailer's reserve volumes of the strategic inventory increase at first and then decrease; product procurement volumes gradually decrease; emergency dispatch volumes remain stable; and expected profits gradually will decrease when the market size is larger or the market size is smaller and the manufacturer's reliability is lower. (3)If the redundancy of the horizontal joint strategic inventory is lower, as the manufacturer's reliability increases, retailer's reserve volumes of the strategic inventory likewise increase at first and then decrease; product procurement volumes gradually will increase when the market shrinkage rate is smaller; emergency dispatch volumes follow the same trend as reserve volumes of the strategic inventory; and expected profits decrease at first and then increase. (4)If the redundancy of the horizontal joint strategic inventory is higher, as the proportion of the manufacturer's post-disruption supply increases, retailer's reserve volumes of the strategic inventory decrease; product procurement volumes gradually increase; emergency dispatch volumes remain stable; and expected profits gradually increase. (5)If the redundancy of the horizontal joint strategic inventory is lower, as the proportion of the manufacturer's post-disruption supply increases, retailer's reserve volumes of the strategic inventory decrease at first and then increase; product procurement volumes will gradually decrease when the manufacturer's reliability is lower or the manufacturer's reliability is higher and the supply proportion is larger; emergency dispatch volumes follow the same trend as reserve volumes of the strategic inventory; and expected profits increase at first and then decrease. (6)If the redundancy of the horizontal joint strategic inventory is higher, as the market shrinkage rate increases, retailer's reserve volumes of the strategic inventory and product procurement volumes both remain stable; emergency dispatch volumes decrease; and expected profits gradually decrease. (7)If the redundancy of the horizontal joint strategic inventory is lower, as the market shrinkage rate increases, retailer's reserve volumes of the strategic inventory decrease; product procurement volumes increase; emergency dispatch volumes follow the same trend as reserve volumes of the strategic inventory; and expected profits gradually decrease.
The follow-up study will attempt to add the manufacturer's decision, and then to compare and analyze the effectiveness of vertical joint strategic inventory and horizontal joint strategic inventory. In addition, the issue of joint decision-making between joint strategic inventory strategy and other coping strategies can be further researched.

Key words: supply disruption, strategic inventory, coping strategies, horizontal alliance