The 3 laws of demand. Elasticity is a useful summary measure of demand.
Price elasticity measures the responsiveness of demand to price changes.
A rule of thumb for calculating elasticity. The difference between a shift of the demand curve and a movement along the demand curve. Changes in income and changes in the prices of related goods shift the demand curve. Price elasticity is related to marginal revenue , and to total revenue. As price increases, the quantity demanded decreases.