贸易差额是指一段时期内有形进口与有形出口总价值之间的差额。若将进口总价值计于一方、出口总价值计于另一方,便可算出贸易差额。因此,如果我们的出口价值超过进口价值,贸易差额在此情况下便对我们有利,因为其他国家欠国家的正是出口与进口价值之间的差额。

The balance of trade is the difference in total value between the visible imports and the visible exports over a period. If we were to calculate the total value of the imports on one side and the total value of exports on the other, we would be able to work out the balance of trade. So if the value of our exports exceeded that of our imports, the balance of trade would, in this case, be in our favour, because other countries owe to the State the difference between the value of the exports and imports.

因此，外国对国家货币的需求，用于购买该国的商品，会超过该国为购买外国商品而对外币的需求。然而，贸易差额并不能真实反映国民经济的状况，因为国民收入不仅限于对外贸易的利润，其他来源的收入也应计入国民收入之中。不过，贸易差额确实能真实反映我们对外贸易的状况。但是，始终致力于使贸易差额保持对国家有利，是不明智的。这是因为国家可能还有其他的考量，比如与其意识形态有关、与该意识形态的传播有关、与工业发展有关、与满足其自身需求有关，或与某个与其有贸易往来的国家的立场有关的政治问题，以及国家如何谋求塑造该立场。这也可能与国际形势及其可能产生的影响有关。在这种情况下，国家的既定意图将优先于实现有利贸易差额的需要。

Therefore, foreign demand for the State’s currency to pay for commodities from the State would exceed the State’s demand for foreign currency to do the same. However, the balance of trade would not reflect the real picture about the state of the national economy. Because the national income is not only restricted to the profits from foreign trade. Other sources of income would also be considered as part of national income. The balance of trade does however reflect the real picture concerning the state of our foreign trade. It would however be unwise to aim to maintain the balance of trade tipped in favour of the State at all times. This is because the State may have other designs related to her ideology, or to the propagation of that ideology, or related to industrial development, or to fulfilling her needs, or to political issues concerning the stance of a country with whom she has trade relations and how she aims to shape that stance. It could also be related to the international situation and what may influence it. In this context, the State’s intended designs would override the need to achieve a favourable balance of trade.