Suppose we consider four different demand curves for four goods, identical except their degree of inferiority. D₁ is a good with fairly elastic demand, a normal good. D₂ is slightly less so probably still a normal good but with a smaller income effect. D₃ is the demand curve for an inferior good, the income effect works against the substitution effect but demand is still downward sloping but quite inelastic. However, D₄ is the demand curve for a Giffen good.

Inferiority for this good is so great that the income effect overwhelms the substitution effect causing the slope of the demand curve to be positive.

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