主题：从萧条到繁荣，再到萧条 -- 西瓜子

In economics, capital, capital goods, or real capital are those already-produced durable goods that are used in production of goods or services. The capital goods are not significantly consumed, though they may depreciate in the production process. Capital is distinct from land in that capital must itself be produced by human labor before it can be a factor of production. At any moment in time, total physical capital may be referred to as the capital stock (which is not to be confused with the capital stock of a business entity.) In a fundamental sense, capital consists of any produced thing that can enhance a person's power to perform economically useful work—a stone or an arrow is capital for a caveman who can use it as a hunting instrument, and roads are capital for inhabitants of a city. Capital is an input in the production function. Homes and personal autos are not capital but are instead durable goods because they are not used in a production effort.