A perverse demand curve, also known as a Giffen good, is a type of economic relationship in which an increase in the price of a good leads to an increase in the quantity demanded. This relationship is the opposite of the normal downward-sloping demand curve that is typically observed in economics, in which an increase in price leads to a decrease in the quantity demanded.

Perverse demand curves are relatively rare, but they can occur in certain situations where the good in question is considered a necessity and has few close substitutes. For example, a household that is struggling to afford food may be willing to buy more of a staple food item, such as rice or bread, if the price increases, as they may view it as a necessity and be willing to cut back on other expenses in order to afford it.

It is important to note that the concept of a perverse demand curve is somewhat controversial in economics, and some economists argue that these relationships may not occur in practice.