when a good is called an inferior good
Inferior good In economics, an inferior good is a good whose demand decreases when consumer income rises (or demand rises when consumer income decreases),[1] unlike normal goods, for which the opposite is observed.[2] Normal goods are those for which demand rises as consumer income rises. [3] This would be the opposite of a superior good, one that is often associated with wealth and the wealthy, whereas an inferior good is associated with lower socio-economic groups.