The quantity of a good or service that consumers are willing and able to buy at given prices in a given period of time. For economists, demand is always effective demand
Effective demand
The desire for a good or service backed by an ability to pay
Market demand
The quantity of a good or service that all the consumers in a market are willing and able to buy at different market prices
Condition of demand
A determinant of demand, other than goods own price, that fixes the position of the demand curve
Increase in demand
A rightward shift of the demand curve
Decrease in demand
A leftward shift of the demand curve
Normal good
A good for which demand increases as income rises and demand decreases as income falls
Inferior good
A good for which demand decreases as income rises and demand increases as incomes falls
Elasticity
The proportionate responsiveness of a second variable to a change in the first variable
Price Elasticity of Demand
The responsiveness of quantity demanded to a change in price of that good. %change in QD / %change in P
Income Elasticity of Demand
The responsiveness of quantity demanded to a change in income. %change in QD / %change in income
Cross Elasticity of Demand
The responsiveness of quantity demanded to a change in price of a different good. %change in QD of good A / %change in price of good B