A change in demand is illustrated by what shift in a graph?

A change in demand is represented by a shift of the demand curve itself. This shift occurs due to various factors that influence consumer behavior, such as changes in income, preferences, prices of related goods, or expectations about the future. Specifically, an increase in demand results in the demand curve shifting to the right, indicating that consumers are willing to purchase more of a good or service at every price level. Conversely, a decrease in demand shifts the demand curve to the left, showing that consumers are willing to purchase less at every price level.

Understanding this concept is crucial because it distinguishes changes in demand from changes in quantity demanded, which are represented by movements along the demand curve in response to price changes. The other options relate to different aspects of economic graphing and do not illustrate a change in demand specifically. For example, a shift of the supply curve pertains to changes in supply rather than demand, and a fixed price level does not indicate any movement in demand or supply. Thus, recognizing that a shift of the demand curve signifies a change in demand helps in analyzing market dynamics effectively.