<div>We consider the models of sequential games over supply chain networks and production chain networks. In the supply chain model, we show that in particular, for series-parallel networks, there is a unique equilibrium. </div><div>We provide a polynomial time algorithm to compute the equilibrium and study the impact of the network structure to the total trade flow at equilibrium. Our results shed light on the trade-off between competition, production cost, and double marginalization. </div><div><br></div><div>In the production chain model, we investigated sequential decisions and delegation options over three agents, chain, and tree networks. Our main contribution is showing the value of delegation and how to maximumly leverage the middleman's aligned interests with the principal. In particular, we provide a polynomial time algorithm to find the optimal delegation structure and the corresponding necessary contract payments for the principal. Furthermore, we analyzed the trade-off of the delegation and gave a deeper insight into the value of delegation in different conditions. Several questions are left for future research such as what's the optimal delegation structures in general tree and how to build the model that agents can try multiple times until the task is successful. </div>

本文以一個簡單賽局理論模型為分析依據,探討企業間的自製或是外包策略對整體社會福利的影響。 傳統經濟理論分析告訴我們自製策略可以解決雙重邊際化的問題。但在本文我們舉出一個反例，亦即當存在研發的可能及上下遊市場的研發外溢效果時，垂直整合可能會造成廠商過度研發的情形，最終產生整體社會福利不效益情形。 / In this paper, we set up a game-theoretic model, in which the whole industry is composed of a downstream monopolist and two upstream firms. This paper discusses the major debate in a firm’s market strategy: to make or to buy the components it needs. Traditionally, economic theories told us that vertical integration strategy (make strategy) can solve the problem of double marginalization and hence increase profits as well as social welfare. Nevertheless, this result does not necessarily hold when R&D possibility is introduced. We show that when there is downstream to upstream R&D spillover, vertical integration may result in an over-investment in R&D from the social standpoint. This result may shed some light on the rationale behind recent antitrust rulings.