What They Are
A Giffen good is a product for which demand rises when the price rises, and falls when the price falls - the opposite of normal behavior. They are named after the Scottish economist Sir Robert Giffen, who noted that during the Irish Potato Famine (1845–1852), as the price of potatoes rose, poor families bought more potatoes, not fewer.
This seems to violate the law of demand (higher price → lower quantity demanded). But it does not. It reveals something about how very poor people allocate their budgets.
How It Works
The mechanism requires three conditions:
- The good is an inferior good - people buy less of it as they get richer (cheap staple food, basic clothing).
- The good accounts for a large share of the budget - a poor family might spend 60–70% of their income on potatoes.
- There are no close substitutes - if potatoes become more expensive, there is no equally cheap alternative.
Now follow the logic. Potatoes become more expensive. A poor family’s income is already stretched. To afford the same number of potatoes at the new price, they must spend more of their income on potatoes. That leaves less money for everything else - meat, vegetables, rent. So they cut back on meat and vegetables to free up money for potatoes. But since they are eating fewer vegetables and less meat, they need even more potatoes to get enough calories. The net effect: they buy more potatoes at a higher price.
This is called the Giffen effect - the income effect (you are poorer because the price went up) overwhelms the substitution effect (you would normally switch to alternatives). The good is such a large part of your budget that the price increase makes you so much poorer that you cannot afford substitutes, and you end up buying more of the now-more-expensive staple.
Why It Matters
Giffen goods are economically important because they clarify the difference between substitution effects and income effects - two forces that determine how people respond to price changes. Most goods have a small income effect and a large substitution effect, so the law of demand holds. Giffen goods show what happens when that balance flips.
They are also a reminder that economic models are descriptions of tendencies, not iron laws. The law of demand is extremely reliable - but it has genuine exceptions under specific conditions.
Are They Real?
For a long time, economists debated whether Giffen goods actually existed or were just a theoretical curiosity. Empirical studies have confirmed them. A 2008 study of rice consumption in poor Chinese households found evidence of Giffen behavior: when rice prices rose, the poorest households bought more rice, not less.
Giffen goods are rare in modern developed economies because the conditions are hard to meet. Few goods take up a large enough share of anyone’s budget. They are a phenomenon of extreme poverty, not of normal markets.
Common Misunderstandings
Not the same as a Veblen good. A Veblen good (luxury watches, designer handbags) also has an upward-sloping demand curve, but for a different reason: people buy more when the price rises because the high price is the point (status signalling). A Giffen good is the opposite - nobody buys potatoes for status. They buy them because they are desperate.
Not the same as a necessity. Necessities like water and electricity have low price sensitivity (inelastic demand), but they do not have the perverse response of Giffen goods. If water prices double, households cut back, not increase.
See also: Supply & Demand, Prices, Markets