Why are nearly all goods superior goods?

Question

i really don't understand

Answer 1

Superior goods make up a larger proportion of consumption as income rises, and as such are a type of normal goods in consumer theory. If the quantity of an item demanded increases with income, but is not enough to increase the share of the budget spent on it, then it is a normal good.

The choice of the word "superior" to define goods of this type suggests that they are the antonym of "inferior goods", but this is misleading; an inferior good can never be a superior good, but many goods are neither.

It is not true that nearly all goods are superior goods. Using the terminology above, nearly all goods are normal goods. However, some texts on microeconomics use the term Superior good as the sole alternative to an inferior good, making "superior goods" and "normal goods" synonymous. Where this is done, a product making up an increasing share of spending under income increases is often called an Ultra-superior good.

Example: Your current monthly income is $2,000. You are spending $1,000 on rent (50% of your budget) and $40 on sushi (2% of your budget). As your income increases to $4,000 you increase your rent expenditures to $1,600 (40% of your budget) and your sushi expenditures to $100 (2.5% of your budget). Rent is a normal good - as your income increases your expenditure on rent increases (from $1,000 to $1,600). Sushi is a superior good - as your income increases, you spend a greater fraction of your budget on it (2.5% instead of 2%).