Comparative advantage Study Guide

📖 Core Concepts Comparative Advantage – Ability to produce a good at a lower relative opportunity cost than another producer. Opportunity Cost – Quantity of another good that must be forgone to produce one unit of a good. Absolute Advantage – Producing more output per unit of input; unrelated to relative costs. Ricardian Model – Two‑country, two‑good world with labor as the only factor; specialization driven by comparative advantage. Autarky Relative Price (Home): $p{C}^{A}=a{C}/a{W}$; (Foreign): $p{C}^{A'}=a{C}'/a{W}'$. World Relative Price with trade: $p{C}^{W}$ lies between the two autarky prices. Terms of Trade – Rate at which one good exchanges for another in the market; settles between the countries’ opportunity costs when each specializes. Specific‑Factors Model – Multiple factors (labor, capital, land) with some immobile; extends Ricardian insight. Heckscher‑Ohlin (H‑O) Model – Comparative advantage arises from differences in factor endowments. New Trade Theory – Adds increasing returns, imperfect competition, and intra‑industry trade to the classic framework. --- 📌 Must Remember Comparative advantage → lower relative opportunity cost, not higher productivity. Gains from trade exist even if one country has an absolute advantage in every good (Ricardo, 1817). Free‑trade price $p{C}^{W}$ must satisfy $p{C}^{A'} < p{C}^{W} < p{C}^{A}$ (or the reverse depending on which country is more efficient). Specialization rule: Each country produces the good for which its $a$ (unit labor requirement) is smaller relative to the other good. In the specific‑factors model, only the mobile factor (labor) reallocates; sector‑specific capital stays put. H‑O prediction: Countries export goods that intensively use their abundant factor. New Trade Theory predicts two‑way trade of similar products due to scale economies. --- 🔄 Key Processes Calculate Opportunity Costs For Home: OC of cloth = $a{C}/a{W}$ (units of wine). For Foreign: OC of cloth = $a{C}'/a{W}'$. Determine Comparative Advantage Compare OC’s; lower OC → comparative advantage in that good. Specialization Decision Each country produces only the good with lower OC. Find World Relative Price Range Identify autarky prices, then locate $p{C}^{W}$ between them. Compute Terms of Trade Set $p{C}^{W}$ so both countries gain: export price > own OC, import price < own OC. Assess Gains Compare post‑trade consumption possibilities (expanded PPF) to autarky consumption. --- 🔍 Key Comparisons Comparative vs. Absolute Advantage Comparative: lower relative cost → basis for trade. Absolute: higher productivity → not required for trade. Ricardian vs. Specific‑Factors Model Ricardian: single mobile factor (labor), constant returns, no factor immobility. Specific‑Factors: multiple factors, some sector‑specific, captures short‑run distribution effects. Heckscher‑Ohlin vs. New Trade Theory H‑O: trade driven by factor‑endowment differences, predicts inter‑industry trade. New Trade: adds economies of scale and product differentiation → explains intra‑industry trade. --- ⚠️ Common Misunderstandings “Comparative advantage means being the best.” Wrong: It’s about relative cost, not absolute productivity. “If a country has an absolute advantage in everything, it should not trade.” Wrong: Even then, specialization yields higher total output and consumption. “Terms of trade equal world price.” Wrong: Terms of trade refer to the exchange rate between two goods, not a single price level. “Specific‑factors model eliminates comparative advantage.” Wrong: It still yields comparative advantage; factor immobility only affects income distribution. --- 🧠 Mental Models / Intuition “Opportunity‑cost seesaw” – Picture each good on opposite ends of a seesaw; the side that drops (lower cost) tells you where the country should sit (specialize). “Price sandwich” – World price is the sandwich filling between two autarky prices; if it moves outside, one country loses. “Factor‑abundance lens” – Imagine a country’s abundant factor as a magnifying glass that makes goods using it look cheaper to produce. --- 🚩 Exceptions & Edge Cases Identical Opportunity Costs – If $a{C}/a{W}=a{C}'/a{W}'$, no comparative advantage; trade may be indifferent. Non‑constant Returns – Ricardian model assumes constant returns; if returns diminish, specialization may be sub‑optimal. Trade Barriers – Tariffs, quotas, or transport costs can push $p{C}^{W}$ outside the “sandwich,” nullifying gains. Factor Mobility Limits – In the short run, labor may not move instantly, altering the realized comparative advantage. --- 📍 When to Use Which Use Ricardian analysis when: Only labor matters, technology differences are captured by unit labor requirements. Use Specific‑Factors when: You need to examine short‑run income effects with sector‑specific capital or land. Use Heckscher‑Ohlin when: Factor endowments (labor vs. capital intensity) differ substantially across countries. Use New Trade Theory when: Explaining trade of similar products (e.g., cars, computers) or the role of economies of scale. --- 👀 Patterns to Recognize “Between‑price” pattern – World relative price always nests between the two autarky prices. “Lower‑a” pattern – The good with the smaller unit‑labor coefficient ($a$) in a country is its export good. “Factor‑intensity” pattern – In H‑O, look for which good uses the abundant factor more intensively; that good is likely exported. “Scale‑economy” pattern – Presence of large fixed costs → expect intra‑industry trade (New Trade Theory). --- 🗂️ Exam Traps Distractor: “The country with the absolute advantage always exports the good it produces most efficiently.” Why tempting: Confuses absolute with comparative advantage. Correct: Export decision follows lower relative opportunity cost, not absolute productivity. Distractor: “Terms of trade are always favorable to the smaller country.” Why tempting: Smaller economies are often thought to have bargaining power. Correct: Terms of trade lie between the two countries’ opportunity costs; size alone doesn’t guarantee favorability. Distractor: “In the Ricardian model, capital is irrelevant.” Why tempting: Model assumes labor only. Correct: Capital is excluded by assumption, not because it has no effect in reality. Distractor: “If two countries have identical $a$ ratios, no trade will occur.” Why tempting: Identical opportunity costs suggest no comparative advantage. Correct: Trade may still arise from other factors (e.g., preferences, transport costs, scale economies). ---