In economics, the general body of wage earners. In classical economics, labour is one of the three factors of production, along with capital and land. Labour can also be used to describe work performed, including any valuable service rendered by a human agent in the production of wealth, other than accumulating and providing capital. Labour is performed for the sake of its product or, in modern economic life, for the sake of a share of the aggregate product of the community's industry. The price per unit of time, or wage rate, commanded by a particular kind of labour in the market depends on a number of variables, such as the technical efficiency of the worker, the demand for that person's particular skills, and the supply of similarly skilled workers. Other variables include training, experience, intelligence, social status, prospects for advancement, and relative difficulty of the work. All these factors make it impossible for economists to assign a standard value to labour. Instead, economists often quantify labour hours according to the quantity and value of the goods or services produced.