What can cause an increase in demand for a good?

An increase in the price of a substitute good can indeed lead to an increase in demand for a particular good. This phenomenon occurs because when a substitute good becomes more expensive, consumers may look for alternatives that offer similar benefits for a lower price. As a result, the demand for the good in question increases, as more consumers choose it over the now pricier substitute.

For example, if the price of coffee rises significantly, consumers who enjoy caffeine might turn to tea, thereby increasing the demand for tea. This shift happens because consumers are motivated to avoid paying the higher price for coffee and thus opt for the more affordable alternative.

The other options highlight scenarios that typically would not result in increased demand. A decrease in consumer income usually decreases demand for most normal goods, as consumers have less purchasing power. An increase in the price of a complementary good, on the other hand, can decrease demand for a product that is usually purchased alongside it, as consumers may be less inclined to buy both. Lastly, no change in market preferences indicates stability, which does not inherently stimulate an increase in demand for any good.