LABOUR, like all other things which are purchased and sold, and which may be increased or diminished in quantity, has its natural and its market price. The natural price of labour is that price which is necessary to enable the labourers, on with another, to subsist and to perpetuate their race, without either increase or diminution.
David RicardoIf I discover a manure which will enable me to make a piece of land produce 20 per cent more corn, I may withdraw at least a portion of my capital from the most unproductive part of my farm.
David Ricardo