What differentiates a movement along the demand curve from a shift in the demand curve?

A movement along the demand curve occurs specifically as a result of a change in the price of the good or service itself. When the price changes, it leads to a change in the quantity demanded, which is represented by moving along the existing demand curve. If the price increases, the quantity demanded typically decreases, and vice versa.

In contrast, a shift in the demand curve happens due to non-price factors, such as changes in consumer preferences, income levels, the prices of related goods (substitutes or complements), or demographic changes. These factors alter the overall demand for a product at every price level, thereby shifting the entire demand curve to the left (decrease in demand) or to the right (increase in demand).

This distinction is central to understanding how markets operate. While movements along the curve relate to responses to price fluctuations, shifts indicate broader trends and changes in consumer behavior that affect demand independent of price.