If the term “commodities” were broad enough to cover all of these
factors, then it might be properly said that the debts of the citizens
of one nation to the citizens of another nation were all covered by
exchange of commodities.
This is so far recognized that it is a common expression to say that
all imports are paid for by exports, because no nation can except for a
limited time pay its commodity trade balance in gold without exhausting
the gold upon which the credit of its currency is based.