橫看成嶺側成峰？──再探「McKenzie-Jones產品三角形」

Different Vistas along with the Same Topography? -- Revisiting the ''McKenzie-Jones Goods Triangle''

在傳統的李嘉圖式分派理論／模型中，我們可以仿造平面座標內兩產品的世界生產可能集合，而繪製出三產品設定下的「產品三角形」，謂之「McKenzie-Jones產品三角形」。該三角形周圍的邊線段落與內部的不同區塊，表達了國家間依照某一修正（機會成本之評比方式）後的比較利益原則，進行要素配置而獲得產品分派的過程及結果。本文採用三國三產品之設定，重新探索此一三角形背後的三度空間錐狀體，藉以說明：我們有必要由看似光滑平順的三角形，回復至原本乃帶有「端點、山脊與琢面」的錐狀體，以利完整地洞察出各國於錐狀體之生產可能集合表層的分工變化狀態，及該三角形內部出現平行四邊形之小區塊的原由。此類回歸至空間（座標值）的詳細推導，足以讓吾人警覺到：由錐狀體化約至平面製圖時，對產品分派有所改變的定性判斷，容易受到誤導；也因此，產品三角形邊線上與內部的移動距離，應避免被施予「基數」式的解讀，特別是其三個邊線的段落均早已被抹平為單一斜率值的直線。

In the traditional Ricardian assignment theory／models, one can sketch the threedimensional world transformation frontier similar to the two countries-two commodities production possibilities curve, and present it as a triangle on the plane. We revisit here one specific and better-not-to-be-forgotten triangle, the so-called ''McKenzie-Jones Goods Triangle'', under the context of three countries-three products setting. By means of both bilateral comparison of opportunity costs and amended principle of comparative advantage, one can easily detect the qualitative direction of change, along any sideline of the Goods Triangle, of commodities production assigned to any country, but it's less clear how the movements inside the interior part of the triangle should be judged and explained. This article tries to answer that vital question by tracing the Goods Triangle back to its original (pentagonal) pyramid with some inherent facets of parallelograms, while reaffirming the alluring complexity of changes in the division of labor on the edges and surface of that pyramid as world production possibilities set. One of the main lessons worth emphasizing might be: it's categorically wrong to regard the movements along the three line segments and／or inside the interior space of the Goods Triangle as cardinal distances; and, paying full attention to some cautionary reminders from Lionel McKenzie and Ronald Jones, we could relieve ourselves of being misled by the triangle stripped of its concrete and tactile pyramid.