Final answer:
Traceability is the ability to trace the history, application, or location of an item. Economists used to track physical items transported between countries to measure the balance of trade.
Step-by-step explanation:
Traceability is the ability to trace the history, application, or location of an item. In the context of measuring the balance of trade between countries, economists used to track the physical items transported by planes, trains, and trucks. They referred to this as measuring the 'balance of trade'. For example, economists would track the quantity and value of goods imported and exported between countries to determine their trade relationships.