In economics, a good whose demand rises as its price rises under a rare theoretical condition is called a Giffen good.
A Giffen good must be an inferior good with a strong negative income effect. When its price rises, a very poor consumer can effectively become poorer and may cut purchases of more expensive foods, increasing consumption of the staple. For this unusual result to occur, the staple must occupy a large share of the budget and have limited close substitutes.
The idea is not the same as a Veblen good. Veblen demand can arise because a higher price signals status or exclusivity, while the Giffen explanation is based on income and substitution effects. The term is also often used loosely for any product with an upward-sloping demand curve, but that usage can hide the strict conditions involved.
Robert Giffen is credited with the nineteenth-century example involving bread and poor households in Ireland, though the historical evidence for that example has been debated. Modern research treats confirmed Giffen behavior as uncommon.