Comparative Advantage

1. The gains from trade rest on comparative advantage, not absolute advantage.
2. A country can gain from trade even if it is absolutely better at producing both goods. What matters is relative opportunity cost: the more productive country cannot make everything at once, so producing one good means sacrificing the other. It should concentrate where its sacrifice is smallest and import the good it is only slightly better at, freeing the partner to make that good where the partner gives up least.
3. When each country specialises in its lower opportunity-cost good, total world output rises, an idea traced to David Ricardo.
4. China holds a comparative advantage in labour-intensive manufacturing while Germany holds it in capital goods such as precision machinery, so specialising and trading raises output in both.

A worked example

1. On a production possibility frontier diagram each country's frontier shows its output limits, and specialisation plus trade lets it consume at a point beyond its own frontier.

Assumptions and limitations

1. The model assumes constant returns to scale and no transport costs.
2. It assumes factors of production move freely within countries but not between them.
3. It assumes only two countries and two goods, with costless, barrier-free trade.
4. In reality transport costs can wipe out a small cost advantage, and tariffs distort the pattern of trade.
5. Comparative advantage is dynamic and can shift as countries invest in skills and capital, e.g. South Korea moved from simple goods to advanced electronics over several decades.
6. Externalities such as pollution are ignored by the model.

Advantages and disadvantages

1. Consumers gain wider choice and lower prices, raising consumer surplus.
2. Firms exploit economies of scale by selling to a larger world market.
3. Greater competition raises efficiency and can transfer technology between countries.
4. Declining sectors can suffer structural unemployment concentrated in particular regions, e.g. US and European steel towns losing out to cheaper imports.
5. A country can become over-dependent on a few trading partners or products and more exposed to external shocks.
6. Trade can bring environmental damage, and the gains and losses are spread unevenly within and between countries.

Should a country specialise on comparative advantage?

1. It holds because specialisation raises world output and living standards, and lets small economies reach a global market and gain economies of scale they could never reach at home.
2. But narrow specialisation, especially in a single primary commodity, leaves a country exposed to price swings and demand shocks, and the theory ignores structural unemployment and environmental costs.
3. On balance the answer depends on how diversified the specialisation is and whether the government supports displaced workers, so partial rather than total specialisation is often wiser.