National comparative advantage is a situation in which a nation can perform an activity or produce a good or service at a lower opportunity cost than any other nation. Imports - the goods and services that we buy from other countries. Exports - the goods ands services that we sell to people in other countries. Other nations may have a national comparative advantage. Nations import when world price is cheaper than the domestic price -> increases quantity bought, decreases quantity produced domestically, price falls to world price. Nations export when world price is higher than the domestic price -> decreases quantity bought domestically (due to higher price), increases quantity produced, price rises. International trade is a win-win game for all countries. Quantity bought increases to quantity demanded at world price. Quantity produced decreases to the quantity supplied at world price. Increase in total surplus from lower prices and increased purchases. Quantity bought falls to quantity demanded at world price.