If you have trouble remembering whether you need to shift or move along the demand curve, helps to recall a lesson from the appendix to Chapter 2. A curve shifts when there is a change in a relevant variable that is not measured on either Because the is on the vertical axis, a change in price represents a move- ment along the demand curve. By contrast, income, the prices of related goods tastes, expectations, and the number of buyers are not measured on either a change in one of these variables shifts the demand curve.