Comparative Advantage Calculator
From the output of two goods, compute the opportunity cost of producing good 1 — and thus who has the comparative advantage.
輸入資料
計算結果
重點速覽：Comparative advantage is when one side has a lower opportunity cost of producing a good. opportunity cost of Good 1 = Good 2 output / Good 1 output. The lower-cost side has the comparative advantage and should specialise and trade for mutual gain. Example: 10 Good 1 or 20 Good 2 → cost of 1 Good 1 = 2 Good 2. WARNING: Simplified two-good model; real trade has transport, scale and many goods. Education, not advice.
計算公式
生產 1 單位商品1 的機會成本 = 商品2 產量 ÷ 商品1 產量。
機會成本較低者，對該商品有比較優勢。
$$\text{Opportunity Cost of Good 1} = \dfrac{\text{Good 2 Output}}{\text{Good 1 Output}}$$使用說明
- Enter the output of Good 1 with all resources.
- Enter the output of Good 2 with all resources.
- View the opportunity cost of producing Good 1.
機會成本與比較優勢範例 (以相同資源可生產的產量計)
| 生產者 | 商品1 產量 | 商品2 產量 | 商品1 的機會成本 (以商品2 計) |
|---|---|---|---|
| 甲國 | 10 | 20 | 2.00 |
| 乙國 | 5 | 20 | 4.00 |
| 丙國 | 8 | 12 | 1.50 |
生產 1 單位商品1 的機會成本 = 商品2 產量 ÷ 商品1 產量。機會成本越低者，對商品1 越有比較優勢。
理財情境案例
案例一：計算機會成本判斷比較優勢
假設甲國以固定資源可生產商品1 共 10 單位，或商品2 共 20 單位 (只能擇一投入或按比例分配)。
生產 1 單位商品1 的機會成本 = 商品2 產量 ÷ 商品1 產量 = 20 ÷ 10 = 2 — 即甲國每多生產 1 單位商品1，就要放棄 2 單位商品2。
若乙國同樣資源可生產商品1 共 5 單位或商品2 共 20 單位，其商品1 機會成本 = 20 ÷ 5 = 4。比較兩者：甲國生產商品1 的機會成本 (2) 低於乙國 (4)，因此甲國對商品1 有比較優勢，應專注生產商品1;乙國則相對地對商品2 有比較優勢。
案例二：專業分工與貿易如何創造互利
延續上例：甲國商品1 機會成本 = 2 (以商品2 計)，乙國商品1 機會成本 = 4。反過來看商品2 的機會成本，甲國為 1÷2 = 0.5 單位商品1，乙國為 1÷4 = 0.25 單位商品1 — 乙國生產商品2 的機會成本較低。
於是甲國專攻商品1、乙國專攻商品2，再互相貿易。只要交換比率落在兩國機會成本之間 (例如 1 商品1 換 3 商品2)，雙方都能得到比自己生產更划算的組合。
這就是李嘉圖『比較優勢』理論的威力：即使一國在所有商品上生產效率都較高 (絕對優勢)，只要各自專注於『機會成本相對較低』的商品並貿易，整體產出與雙方福利都能提升 — 貿易並非零和，而是互利。
常見問題
What is comparative advantage, and how does it differ from absolute advantage?
Absolute advantage (Smith) is about who produces more or more efficiently with the same resources. Comparative advantage (Ricardo) is about who has the lower opportunity cost. Even if one country is absolutely better at everything, trade still helps both as long as their opportunity costs differ — each specialises where it gives up least.
How do I compute the opportunity cost and decide who has the advantage?
Opportunity cost of 1 unit of Good 1 = Good 2 output / Good 1 output; of Good 2 = Good 1 / Good 2. Compare across the two sides: the lower cost side has the comparative advantage in that good. In a two-good, two-party model, if A has the advantage in Good 1, B must have it in Good 2.
What is the real-world meaning and limits of the theory?
It is the key argument for free trade and division of labour — specialisation lifts total output so all can consume more. But it is a stylised model (two goods, mobile resources, no transport, fixed tech); it ignores distribution (some sectors/workers lose), scale economies and dynamic advantage. Useful as the starting point, not the whole policy story.
How is comparative advantage different from absolute advantage?
Absolute advantage compares efficiency (who makes more). Comparative advantage compares opportunity cost (who gives up less). The non-intuitive but crucial result: a country can have an absolute advantage in everything yet still gain from trade, because it cannot have a comparative advantage in everything — specialising where its cost is lowest leaves the other good to the partner.
Why is trade not a zero-sum game?
Because specialisation by comparative advantage makes the total pie bigger, not just redistributes it. Each side trades at a rate between their opportunity costs and ends up able to consume more than under self-sufficiency. The gains are real overall, though some industries or workers may need adjustment support.
相關工具
參考資料
內容審核：香港計算器財經團隊。計算邏輯與公式參考香港金融管理局（HKMA）及投資者及理財教育委員會（IFEC）之個人理財計算指引，結果僅供參考，實際以相關機構公佈為準。