以利潤最大化為目標之最適貨櫃船型模式之研究

Abstract

貨櫃船運輸興起至今，定期貨櫃船之經營已取代傳統雜貨船，成為海運市場的主流。過去二十多年來，由於港埠貨櫃化程度提高，貨櫃裝卸效率提昇，與造船科技的進步，全球主要航線上貨櫃船型的發展有逐期逐漸增大的趨勢（McLellen,1997），貨櫃船大型化對海運市場主要有兩向顯著意義：軸輻路網（Hub-and-Spoke Networks）經營型態的建立，與航商單位運送成本的下降。 文獻中對船舶經濟規模的研究，例如Jannson and Shneerson(1982)、董孝行（民國75年）、Talley(1990)、Lim（1994）與McLellan（1997）等，其目標函數多為單位成本最小化，而且只考慮船型變動對成本的影響。然而基本上，航商追求的目標是利潤最大，利潤等於運費收入減去營運成本；船型增大與船速加快都會增加成本，但也會增加運費收入，關鍵則在能否增加利潤。 本研究即嘗試構建『以利潤最大化為目標之模式』分析最適貨櫃船型，在航線給定的前提下，探討何等船型與船速能使航商獲得最大的利潤。研究方法採用迴歸分析，建立各項成本相對於船型及／或船速的迴歸式，利用各項迴歸式即可建立利潤目標式，再利用非線性規劃方法求解之，可求得最適船型與船速的組合。模式中同時將船型與船速納入考量，其分析功能將更為具體實用。 本研究所構建之目標函數一如預期，為一嚴格凸向上函數（strictly concave function）。主要結論為航商若要追求最大利潤，朝向船型愈大愈佳的趨勢，船速則不需快。

Since the rise of containerization, containerships have become major players, instead of general cargo ships, in the liner shipping market. Over last two decades, due to the upgrade of the port containerization and efficient handling of containers, and the technology of ship building, the size of the containerships on the main routes increases in every ten-year period (McLellan, 1997). There are two significant meanings for using large containerships in the ocean transportation market: the establishment of hub-and-spoke networks and the decrease of the unit transportation cost. Most of previous researches in scale economies of ships, such as Jannson and Shneerson (1982), Talley (1990), Lim (1994) and McLellan (1997), focused on the goal of minimizing the unit operation cost, and the influence of changing ship size on the operation cost. However, what shipowners pursuing is to maximize the profit, which equals revenue minus operation cost. Bigger ships or faster speed will increase not only operation cost but also the revenue. The key point is whether the resulting profit can be increased or not. This paper attempts to formulate a profit maximization model for analyzing the optimal containership size, given the route of ships, to determine the optimal size and/or speed of ships to earn the maximum profit for shipowners. The methods of research are regression analyses of ship costs, which establish the size and/or speed regression functions to the ship costs. And then the objective function can be formulated, whose optimal solution can be solved by nonlinear programming methods. This model takes ship size and speed into account, and hence can reach a more concrete and practical result than those before. The objective function is a strictly concave function as expected. The main conclusion is that when shipowners pursuing a maximizing profit, the bigger ship size is better and the speed of ship is allowed to be slower.