Giffen Good

A Giffen good is a theoretical and empirically rare category of good for which demand increases as its price rises, contradicting the typical downward-sloping demand curve. The concept is named after Victorian-era Scottish economist Sir Robert Giffen, to whom Alfred Marshall attributed the observation in the 1895 edition of Principles of Economics, citing the behavior of poor households purchasing more bread as its price climbed.

The mechanism rests on the interaction of two effects from consumer theory:

• Substitution effect: When a price rises, consumers normally shift toward cheaper alternatives.
• Income effect: A price rise effectively lowers real income.

For a Giffen good, three conditions must hold simultaneously: (1) the good is inferior (demand falls as income rises); (2) it constitutes a large share of the consumer's budget; and (3) few close substitutes are available. When the price of such a staple rises, the negative income effect — making the household poorer — overwhelms the substitution effect, forcing consumers to buy more of the cheap staple and cut back on costlier alternatives like meat or vegetables.

Empirical confirmation has been elusive. The most cited modern evidence comes from a 2008 field study by Robert Jensen and Nolan Miller, "Giffen Behavior and Subsistence Consumption" (American Economic Review, Vol. 98, No. 4), which documented Giffen behavior for rice in Hunan and wheat (mantou) in Gansu among very poor Chinese households. Earlier claims about the Irish Potato Famine (1845–1849) have been largely rejected by economic historians, including Gerald Dwyer and Cotton Lindsay (1984).

For policy researchers, the Giffen concept matters in food security analysis, subsidy design, and poverty economics: removing a price support on a staple consumed by the very poor can, in narrow circumstances, reduce its consumption rather than increase it. It is distinct from a Veblen good, where demand rises with price due to status signaling rather than subsistence constraints.