2.1.7—Shifts vs movements

A movement along demand or supply follows a change in the good’s own price. A shift changes the entire curve because another determinant changes.

Ask two questions: did the product’s price change, and did willingness to buy or sell change at every price? The second indicates a shift.

A higher coffee price moves consumers up the same demand curve; a change in the price of tea, a substitute, shifts coffee demand.

Do not draw an arrow along a curve when the question changes income, costs, tastes or technology; those are shift factors.