What factors can shift the demand curve?

The demand curve represents the relationship between the price of a good and the quantity demanded by consumers. Several factors can lead to a shift in this curve, indicating that consumers are willing to buy different quantities at each price level. Consumer preferences play a significant role; for instance, if a product becomes more fashionable or desirable, demand for that product will increase, shifting the curve to the right.

Income levels also impact demand. An increase in consumer income typically leads to an increase in demand for normal goods, while demand for inferior goods may decrease. Additionally, the prices of related goods—complements and substitutes—affect demand. If the price of a substitute good rises, consumers might look to switch to the relatively cheaper option, increasing demand for that good and shifting its demand curve outward.

Understanding these factors helps to illustrate how consumer behavior changes can influence the market and how demand can fluctuate independent of price changes alone. Other answer choices focus on supply-side factors or external influences, which primarily affect the supply curve rather than the demand curve itself.