Benefits of International Trade: IB Economics 4.1 notes

Why countries trade at all

No country can produce everything it wants with its own land, labour and capital. International trade lets a country consume beyond its own production possibilities by specialising in some goods and importing the rest. This links directly to the key concepts of scarcity, choice and interdependence.

The core claim of trade theory is that specialisation according to advantage raises total world output. When each country produces what it is relatively best at and exchanges the surplus, both partners can end up consuming more of every good than they could in self-sufficiency (autarky).

Absolute vs comparative advantage

A country has an absolute advantage in a good when it can produce more of it from the same resources than another country. A country has a comparative advantage when it can produce the good at a lower opportunity cost, meaning it gives up fewer units of the other good.

Absolute advantage explains why a country produces something at all; comparative advantage explains the pattern of trade. This is the key result: even a country that is worse at making everything (no absolute advantage in anything) still gains by specialising where its opportunity cost is lowest.

Worked two-country example (HL)

Take two countries, A and B, each able to devote all resources to wheat or cars. With full resources, A can make 120 wheat OR 60 cars; B can make 40 wheat OR 40 cars. A has an absolute advantage in both goods.

Opportunity costs decide specialisation. For A, one car costs 120/60 = 2 wheat. For B, one car costs 40/40 = 1 wheat. B gives up less wheat per car, so B has the comparative advantage in cars. By the mirror logic A gives up only 0.5 cars per wheat against B's 1 car per wheat, so A specialises in wheat.

Now let A make 120 wheat and B make 40 cars, and agree terms of trade of 1 car for 1.5 wheat (between the two opportunity-cost ratios). Suppose B ships 20 cars to A for 30 wheat. A ends with 90 wheat and 20 cars; producing 20 cars alone would have left A only 80 wheat, so A gains 10 wheat. B ends with 20 cars and 30 wheat; producing 30 wheat alone would have left B only 10 cars, so B gains 10 cars. Both consume beyond their own PPC.

The gains only exist because the opportunity-cost ratios differ. If both countries had identical ratios, there would be no comparative advantage and no gain from specialising.

Sources of comparative advantage

Comparative advantage comes from differences in factor endowments: a country rich in fertile land (New Zealand, dairy), cheap labour (Bangladesh, garments), skilled labour (Germany, engineering) or capital and technology (South Korea, semiconductors) will be relatively cheap at goods that use its abundant factor intensively.

It also comes from climate and natural resources (Saudi oil, Ethiopian coffee), differences in technology and productivity, and economies of scale that reward whoever produces at large volume first. Because these change over time, comparative advantage is dynamic, not fixed.

Other gains beyond output

Trade also lowers prices and widens consumer choice, raises competition which pushes domestic firms toward efficiency, and gives firms access to larger markets so they can reap economies of scale. It spreads technology and ideas across borders and can support the key concept of economic well-being.

A real-world illustration: Bangladesh built a garment export sector on its comparative advantage in low-cost labour, and ready-made garments now make up around 80 percent of its export earnings, funding imports of machinery and food it does not produce cheaply itself.

Limitations of the theory

The simple model assumes no transport costs, perfect factor mobility, constant returns to scale and no trade barriers, none of which hold fully in reality. It also treats the two-good, two-country world as static, ignoring that a country locked into low-value primary exports may face falling terms of trade and volatile prices.

Full specialisation is risky: relying on one export leaves a country exposed to a demand collapse or a bad harvest (an argument for diversification). Trade can also widen inequality within a country, since the factor a country exports gains while import-competing workers can lose, which raises the key concept of equity.

How this is examined

• On Paper 1 (a) parts, define absolute and comparative advantage with a clear opportunity-cost sentence and draw a labelled PPC or trade-triangle; markers reward the opportunity-cost calculation, not just the definitions.
• In HL numeric questions always show the opportunity-cost arithmetic explicitly (e.g. 120/60 = 2 wheat per car); a correct answer with no working loses method marks.
• For evaluation, attack the assumptions: no transport costs, perfectly mobile factors, constant returns, and the risk of over-specialisation, rather than just listing 'unrealistic'.
• Use a real export example (Bangladesh garments, New Zealand dairy) as your named real-world example; generic 'some countries' phrasing scores lower.

Key terms

comparative advantageabsolute advantageopportunity costspecializationfree tradeterms of trade