Final answer:
Three factors strongly influence patterns of international trade: size of economy, geographic location, and history of trade. The economic growth and relative prices in other countries also heavily affect demand for a nation's exports.
Step-by-step explanation:
Three factors strongly influence a nation's level of trade: the size of its economy, its geographic location, and its history of trade.
Large economies like the United States can do much of their trading internally, while small economies like Sweden have less ability to provide what they want internally and tend to have higher ratios of exports and imports to GDP. Nations that are neighbors tend to trade more, since costs of transportation and communication are lower.
Moreover, some nations have long and established patterns of international trade, while others do not.
Two sets of factors can cause shifts in export and import demand: changes in relative growth rates between countries and changes in relative prices between countries.
What is happening in the countries' economies that would be purchasing those exports heavily affects the level of demand for a nation's exports.
For example, if major importers of American-made products like Canada, Japan, and Germany have recessions, exports of U.S. products to those countries are likely to decline. Conversely, the amount of income in the domestic economy directly affects the quantity of a nation's imports: more income will bring a higher level of imports.