Smith argued that people are naturally selfish. This is a good thing, he said, because everyone looks for the kind of work best for them, and this benefits everyone. Balance of trade Countries trade with each other to earn money to buy food and things they can't make themselves. Some people favour free trade, which means there are no restric-tions at all on what goods and services are traded. Most countries use a mixture of both ideas.
Countries measure the success of their trade by their balance of payments.
Invisible earnings are pay-ments for services such as banks and hotels. Visible earnings are for goods you can pack up, such as coal or radios. If someone wants to start a business, they may get money to start by selling shares in the business. Anyone who buys a share partly owns the business and gets some of the profits. The value of shares goes up and down according to how well the business is expected to do.