Where there is scarcity, choices must be made! Scarcity refers to the finite nature and availability of resources while choice refers to people’s decisions about sharing and using those resources. The problem of scarcity and choice lies at the very heart of economics, which is the study of how individuals and society choose to allocate scarce resources.

When the price ratio between items changes this can induce a change in consumption. The part of such a change in consumption that is attributable purely to the change in the price ratio (and not to the associated change in purchasing power) is known as the substitution effect. The remaining part of the change in consumption that is not directly due to the change in the price ratio but is rather brought about by the change in purchasing power is known as the income effect.

One of the most fundamental tenets of economics. Supply refers to the quantity of a product being produced, and demand the quantity consumers wish to buy. In its most basic form, it refers to the theory that the price for a good or service will eventually settle at a point when its demand and its quantity are equal (assuming all other factors remain equal). This is referred to as the equilibrium.