When the demand for a good increases and the supply of the good remains unchanged, consumer surplus
decreases.
Consumer surplus is the difference between the maximum price that a consumer is willing to pay for a good or service and the actual price that they pay. When the demand for a good increases and the supply of the good remains unchanged, the market price of the good will increase. As a result, consumers will have to pay a higher price to purchase the good, which decreases their surplus. This occurs because some consumers who were previously able to purchase the good at a lower price may no longer be able to afford it, and those who do still purchase it will now have to pay a higher price, reducing their surplus.