Final answer:
The demand curve for inferior goods still typically slopes downward, despite their unique characteristic of increased demand when income falls. Critical economic concepts such as the income effect and substitution effect must be considered, which generally do not result in an upward sloping demand curve for these goods.
Step-by-step explanation:
The demand curve for inferior goods does not necessarily have an upward slope. Although consumers may purchase more of an inferior good when the price falls and less when the price rises, this behavior does not imply an upward sloping demand curve. The assumption that demand curves for inferior goods should slope upward neglects two critical concepts in economics: the income effect and the substitution effect. These effects often work in opposite directions. For an inferior good, as income increases, demand decreases, which is reflected in a demand curve that shifts to the left but still slopes downward. When prices change, the substitution effect (the change in consumption patterns due to a change in the relative prices of goods) might still lead to the standard downward slope for the demand curve of an inferior good.