The paper that we are using each day starts as wood on a tree very far from here. Men and machines make the wood into paper in a factory, which people have to carry by trucks and put into stores. At every step in the process the factory has to pay people for their work. And the factory has to use money for buying and repairing the machines, and so on. Of course, everyone concerned has to make profit, too. Even a very simple thing like a piece of paper has a long story behind it. Economists try to understand how all the parts of the long story are related.