Simply stated, economic theory says as your income goes up, you buy less of an inferior
good ("inferior" is not used as a comparison here; it does not have the negative
connotations in economics that it has in English). Ramen
and hamburger helper
are often considered inferior goods (because if you had more money you might choose to go to a restaurant or buy higher-quality food instead.) This does not mean that if you were wealthier you would never eat Ramen again (unless you are like me and live in a dorm and never never
never want to see it again), it simply means you would probably buy less of it if your income rose. A normal good
is the opposite of an inferior good (I would buy a better computer if I had more money, so computers are a normal good for me.)
Technically, an inferior good is one which has a negative income elasticity of demand. (Normal goods have a positive income elasticity of demand.) The derivative of demand for the good with respect to income (d(good)/d(income)) will be negative if inferior (positive if normal). Most firms would rather produce products with higher elasticity of demand because incomes tend to rise over time.