The human work carried out to produce a good or service, and the people that perform that work. Labour is one of the four factors of production in basic macro-economics, along with land, capital and enterprise. Labour supply and demand theoretically determine the level of wages in a particular industry, though minimum wage regulations and collective bargaining agreements between employers and trade unions also have a big influence on the labour market. Labour supply, which is the available workforce (labour force) in an economy, may vary according to seasonal factors - it rises for instance at the end of the academic year when school-leavers are looking for work. Demand for labour however can be seasonal and/or cyclical.