For example, assuming a worker in Germany can either produce 600 machines or 600 tons of tomatoes while a worker in Thailand can either produces 350 machines or 1500 tons of tomatoes per year. An analysis of this scenario reveals that Germany has an absolute advantage over Thailand as far as production of machines is concerned, while Thailand has absolute advantage over Germany as far as production of tomatoes is concerned. Speaking from this perspective, Smith’s theory of absolute advantage postulates that the two countries need to reduce the barriers to trade between each other, thus allowing them to trade with each other based on the commodities they have absolute advantage in. In this case, while Germany needs to reduce trade barriers towards tomatoes that come from Thailand since it has no absolute advantage in tomato production, Thailand needs to remove tariffs on machines from Germany since it lacks absolute advantage as far as machine production is concerned.
例如，假设德国工人每年可以生产600台机器或600吨西红柿，而泰国工人每年可以生产350台机器或1500吨西红柿。对这一情景的分析表明，就机器生产而言，德国比泰国拥有优势，而就番茄生产而言，泰国比德国拥有优势。从这个角度讲，史密斯的优势理论假设两国需要减少彼此之间的贸易壁垒，从而允许它们在拥有优势的商品基础上进行贸易。在这种情况下，虽然德国需要减少对来自泰国的西红柿的贸易壁垒，因为它在西红柿生产方面没有优势，但泰国需要取消来自德国的机器关税，因为它在机器生产方面缺乏优势。
One of the critical issues that emerge as far as the extent to which absolute advantage provides a substantive basis for arguments in support of free trade is the fact that for such arguments to hold, there is a need to consider other factors that could impact free trade apart from the element of production specialisation. In reference to Baier and Bergstrand (2001), despite possessing absolute advantage in the production of certain commodities, countries need to find ways of ensuring their commodities reach the target market. In other words just as in the case of individual businesses, countries too need to consider transport as one of the major costs that could promote and inhibit international free trade regardless of their absolute advantage. For example, in the earlier case of Germany and Thailand, whereas Germany lacks absolute advantage in the production of tomatoes, it can opt to import tomatoes from a country such as China due to lower transport costs as compared to Thailand that could have a higher transport costs. In such a case, whereas Germany may find tomatoes from China cheaper as compared to tomatoes from Thailand, China may not find it necessary to import machines from Germany because of its ability to produce its own machines at a cheaper cost. In such cases, while Germany may eliminate both tariff and non-tariff barriers on tomatoes from China, the Chinese government may continue imposing tariff and non-tariff barriers on machines from Germany since it is capable of producing its own machines at a cheaper cost.
在优势为支持自由贸易的论据提供实质性基础的程度上，一个关键问题是，对于这样的论据，需要考虑除生产要素专业化之外，会影响自由贸易的其他因素。关于Baier和Bergstrand（2001年），尽管在某些商品的生产方面拥有优势，但各国需要找到确保其商品到达目标市场的方法。换言之，就个别企业而言，各国也需要考虑运输作为主要的成本之一，而不管它们的优势如何，它们都可以促进和抑制国际自由贸易。例如，在德国和泰国的早期案例中，尽管德国在番茄生产方面缺乏优势，但它可以选择从中国这样的进口番茄，因为与运输成本较高的泰国相比，运输成本较低。在这种情况下，德国可能会发现来自中国的西红柿比来自泰国的西红柿便宜，但中国可能没有必要从德国进口机器，因为它能够以更低的成本生产自己的机器。在这种情况下，虽然德国可能会取消对来自中国的西红柿的关税和非关税壁垒，但中国政府可能会继续对来自德国的机器实施关税和非关税壁垒，因为它能够以更低的成本生产自己的机器。
Speaking from this point of view, despite the fact that the theory of absolute advantage strongly promotes free trade, Adam Smith cautions that this can only be done when the two or more countries engage in free trade agreement that have varying levels of absolute advantage. Notably, Brecher, Chen and Choudhri (2002) and Schumacher (2012) agree that the support of free trade arguments based on absolute advantage is only consistent in scenarios where countries possess superior advantages over their competitors in one way or the other, having factored in transportation among other factors. Their arguments are inclined toward the fact that two or more countries can have the identical absolute advantages when other factors such as transport are factored in their import-export economics models. In such scenarios, these countries are unlikely to engage in free trade since there are no incentives such as lower prices to motivate them import certain products from their competitors. This implies that when considering absolute advantage as a recipe for free trade, policymakers need to consider other factors such as the location of the country among other factors. On the other hand, the absolute advantage theory has weak arguments for free trade where a country has absolute advantage in different commodities that far outweighs a country that only specialises in the production of one of these commodities (Gupta, 2014). In such scenarios, the ability of the absolute advantage theory to promote free international trade is limited. Thus the absolute advantage theory is only able to provide substantive basis for arguments in support of free trade as long as the trade scenario involves only two countries trading two homogenous products that has a homogenous taste, and the only cost involved in the production of these commodities is the labour cost.
从这一角度讲，尽管优势理论有力地促进了自由贸易，但亚当·斯密警告说，只有当两个或两个以上的签订了具有不同程度优势的自由贸易协定时，这一点才能实现。值得注意的是，Brecher、Chen和Choudhri（2002年）和Schumacher（2012年）同意，基于优势的自由贸易论点的支持仅在以一种或另一种方式拥有优于其竞争对手的优势，并考虑到运输等因素的情况下是一致的。他们的观点倾向于这样一个事实，即当在进出口经济模型中考虑运输等其他因素时，两个或两个以上的可以拥有相同的优势。在这种情况下，这些不太可能参与自由贸易，因为没有诸如降低价格之类的激励措施来激励它们从竞争对手进口某些产品。这意味着，当考虑到优势作为自由贸易的配方时，政策制定者需要考虑其他因素，如在其他因素中的位置。另一方面，优势理论对自由贸易的支持不足，因为一个在不同商品上拥有优势，远远超过了只专注于其中一种商品生产的（Gupta，2014）。在这种情况下，优势理论促进自由国际贸易的能力是有限的。因此，优势理论只能为支持自由贸易的论点提供实质性基础，只要贸易情景只涉及两个贸易两种口味相同的同质产品，并且生产这些商品的成本是劳动力成本。
The theory of comparative advantage 比较优势理论
Another theory that is often used to promote free trade among different countries across the globe is the comparative advantage theory. This theory was formulated by David Ricardo in his work on international trade that was published in 1817. In reference to Watson (2017), Ricardo argues that countries can still effectively engage in international trade even when they have no absolute in the production of their commodities. Arguably, Ricardo emphasises that trade between two or more countries occurs when they do not have a consistent relative productivities. According to Sunley and Martin (2017), the argument that Ricardo promotes in his comparative advantage theory are anchored on the opportunity costs, where a country that absolute advantage in a number of commodities is likely to give up on the production of one or two of these commodities in order to enhance the production of the commodity that has the highest level of benefits or rather returns. For example, whereas both the United States and Mexico can both produce computers and corn, the opportunity cost of producing corn in the United States is far much higher as compared to the opportunity costs of producing this commodity in Mexico. On the other hand, the opportunity cost of producing computers for Mexico is far higher than for the United States. Speaking from this perspective, the United States and Mexico are better off producing computers and corn respectively.
另一个经常被用来促进全球不同之间自由贸易的理论是比较优势理论。这一理论是由大卫·里卡多在1817年出版的《国际贸易著作》中提出的。在提到Watson（2017）时，Ricardo认为，即使各国在其商品生产中没有优势，它们仍然可以有效地参与国际贸易。可以说，里卡多强调，两个或更多之间的贸易发生在它们没有一致的相对生产率时。根据Sunley和Martin（2017年）的观点，里卡多在其比较优势理论中提出的论点基于机会成本，一个在若干商品上拥有优势的可能会放弃生产其中一种或两种商品，以提高收益或回报更高的商品的生产。例如，尽管美国和墨西哥都能生产计算机和玉米，但在美国生产玉米的机会成本远高于在墨西哥生产这种商品的机会成本。另一方面，墨西哥生产计算机的机会成本远远高于美国。从这个角度讲，美国和墨西哥分别生产电脑和玉米的情况更好。