Comparative advantage says two countries gain from trading even if one is better at producing everything, as long as each specialises in what it gives up the least to produce.
Gains from trade ∝ |opportunity-cost gap|
Flow_effective = Flow_potential * (1 - tariff)
ΔGDP ∝ Σ trade_volume_i - deadweight_loss(tariff)
- Tariff rate — an import tax that throttles the flow of goods between countries; higher tariffs shrink the animated cargo stream and the trade-volume stat.
- Comparative advantage gap — how different the two economies' relative production costs are; a bigger gap means more potential gain from specialising and trading.
- Shipping capacity — how many ships/planes can be in transit at once, capping the physical throughput of the route network.
The globe shows cargo tokens flowing along greatcircle-style routes between three stylised economies; raising the tariff slider visibly slows the flow and drags down the trade-volume and GDP-impact stats, while a wider comparative-advantage gap raises the "natural" flow rate absent tariffs.