Final answer:
The potential trade ratios between countries are defined by three factors: the size of their economy, their geographic proximity to trading partners, and their history of international trade. Large economies might trade less proportionally than smaller ones that cannot meet all their needs internally, and nations with a tradition of trade and close neighbors trade more.
Step-by-step explanation:
Three key factors determine whether a nation will have a higher or lower share of trade relative to its Gross Domestic Product (GDP): the size of its economy, its geographic location, and its history of trade. Large economies, such as the United States, can often accommodate a substantial portion of their trading internally, which can result in a lower ratio of exports and imports to GDP. On the other hand, smaller economies, like Sweden, have a limited ability to produce everything they need internally and hence have a higher trade ratio. Moreover, countries with nearby trading partners tend to engage in more trade, due to reduced transportation and communication costs.
Additionally, nations with a long history of foreign trade are more likely to have established patterns of international commerce, influencing their trade levels. Conversely, countries that have historically sought to inhibit trade, like Brazil and India in recent decades, show lower trade levels.