Because the income effect can be positive or negative,a price change can have a small or a large effect on quantity demanded. Giffen good(佶吉芬物品)-Good whose demand curve slopes upward because the (negative)income effect is larger than the (positive) substitution effect. ❑ Because the income effect can be positive or negative, a price change can have a small or a large effect on quantity demanded. Giffen good(吉芬物品)-–Good whose demand curve slopes upward because the (negative) income effect is larger than the (positive) substitution effect