Which factor shifts the demand curve to the left?

A decrease in consumer purchasing power leads to a leftward shift in the demand curve because it reduces consumers' ability to buy goods and services. When purchasing power decreases, either through a decline in income or an increase in prices without a corresponding increase in income, consumers face tighter budgets. This often results in them being less willing or able to purchase the same quantity of a good or service as they would when they have more purchasing power.

The demand curve represents the relationship between price and the quantity demanded. If consumers cannot afford to buy as much, or if they decide to buy less in response to their reduced purchasing power, the overall demand at various price levels shifts to the left. Consequently, at each price point, the quantity demanded decreases, signifying a contraction in demand.

This understanding is essential for evaluating market dynamics, as shifts in demand can affect pricing strategies, production levels, and overall economic health. The other factors mentioned, like increases in income or the number of consumers, typically lead to an increase in demand or a rightward shift rather than a decrease.