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Chinese Journal of Management Science ›› 2025, Vol. 33 ›› Issue (10): 76-85.doi: 10.16381/j.cnki.issn1003-207x.2022.2442

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Production/Inventory Competition Between Firms with Fixed-Proportions Co-production Systems and Aggregate Demands

Shuang He1,2, Liang Zhao1, Jian Zhang1,2(), Lin Li1   

  1. 1.School of Business Administration,Inner Mongolia University of Finance and Economics,Hohhot 010060,China
    2.Doing Business and High-Quality Development of Private Enterprises,Hohhot 010060,China
  • Received:2022-11-09 Revised:2024-07-06 Online:2025-10-25 Published:2025-10-24
  • Contact: Jian Zhang E-mail:bjtuzj@bjtu.edu.cn

Abstract:

The fixed-proportion co-production system (FPCS), which produces two products in fixed proportions by processing a raw material, is widely observed in oil refining, agricultural product processing, chemical industry and so on. In practice, many manufacturers with FPCS are face the challenging problem of mismatches between the fixed-proportion yields and the independent uncertain demands for different petroleum products. In this paper, the production/inventory game of two manufacturers with FPCS is studied. The unmet demand of one manufacturer’s product can be met by the other manufacturer’s leftover stock of the same product, if available, and is lost otherwise. The manufacturers compete for the substitute demands by choosing their own purchase/processing quantities.The problem is formuated as a multi-product multi-period game in which the aggregate demands and the market shares for the two manufacturers’ products are uncertain and independent. It is shown that the production/inventory game is submodular and the response functions are contraction maps, so the existence of a unique Nash equilibrium is guaranteed. It is found that the best response function is strictly decreasing in the rival’s decisions and decreasing in the initial inventory levels of the two products. It is shown that the produce-up-to policy is the equilibrium policy. The impact of competition is examined by showing the equilibrium processing quantity and payoffs are increasing with substitution rates. Finally, we show that our work can be extended to the infinite-period case. The numerical studies are conducted to show the value of our model, and the impacts of some parameters on the equilibrium policies and the players’ payoffs. The managerial insights is also generated from the research findings:(1) Considering the influence of a fixed output ratio, in each period, a high initial inventory level of a certain co-product will put the manufacturer at a disadvantage in the competition in the markets of other co-products. A high initial inventory level of a certain co-product held by the competitor means that the manufacturer can obtain a larger share in the markets of other co-products.(2) An increase in the substitution rate of a certain co-product will lead to an increase in the total quantity of products in the markets of other co-products and a decrease in the substitution demand due to stock-outs, thus reducing the intensity of competition.(3) The manufacturer’s equilibrium processing quantity decreases as the initial inventory levels of its own and competitor’s co-products increase. The traditional produce-up-to strategy is not applicable in a competitive setting. The improved equilibrium strategy in the form of produce-up-to depends on the beginning inventory levels of various co-products of both the competitor and the manufacturers itself.These results have important implications for the competing strategies of the manufacturers with FPCS.Compared with the existing literature, we make the following contributions:(1) the inventory competition games between two manufacturers are studied for the multi-period (finite and infinite) cases, under the co-production system;(2) The concavity and submodularity of the payoff functions, and the existence and uniqueness of the equilibria of the games are shown;(3) For the multi-period (finite, infinite) cases, it is shown that the Nash equilibrium policies have a simple structure (the produce-up-to policy).

Key words: co-production system, fixed yield proportions, substitution competition, processing game, multi-period

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