Match the method with its key metric:
Trade Balance ↔️ Exports - Imports
Export Market Share ↔️ \frac{Country Exports}{Total World Exports} \times 100\%
Unit Labor Costs ↔️ \frac{Total Labor Costs}{Total Units Produced}
Relative Productivity ↔️ \frac{Productivity of Country A}{Productivity of Country B}