What signifies a decrease in supply or demand on a graph?

A decrease in supply or demand on a graph is indicated by a leftward shift of the respective curve. This leftward movement reflects a reduction in the quantity supplied or demanded at every price point. For instance, when the supply curve shifts to the left, it signifies that producers are willing and able to sell less of a good or service at each price level, often due to factors like rising production costs or resource shortages.

Similarly, a leftward shift in the demand curve indicates that consumers are willing and able to purchase less at every price, potentially due to changes in consumer preferences, a decrease in income, or the availability of substitutes. In both cases, moving the curve to the left visually represents that the overall quantity in the market decreases, which is a fundamental concept in understanding supply and demand dynamics.