Normal Good
What is Normal Good?
A normal good is a good for which demand increases when consumer income rises and falls when income decreases.
For normal goods, there is a positive relationship between income and demand. As consumers' incomes rise, they buy more of these goods, and vice versa. Examples include high-quality food, clothing, and electronics.
Normal Good: a worked example
Kai's monthly income rises from $2,400 to $2,760, an increase of $360 on $2,400, or 15%. His restaurant meals go from 8 per month to 10, an increase of 2 on 8, or 25%. Income elasticity of demand is 25% divided by 15%, which equals 1.67. The value is positive, so restaurant meals are a normal good for Kai, and because it exceeds 1 they are a luxury within that group. Over the same stretch his instant noodle purchases fall from 12 packs to 9, a decrease of 3 on 12, or 25%. That gives -25% divided by 15%, or -1.67, and the negative sign marks noodles as an inferior good. The sign does the classifying, while the magnitude only sorts normal goods into necessities below 1 and luxuries above 1.
The mistake students make with normal good
Students treat normal versus inferior as a verdict on quality, assuming anything cheap must be inferior and anything premium must be normal. The classification rests only on the sign of income elasticity for one buyer over one income range. Bulk rice can be normal for a household earning very little and inferior for that same household after a raise, so the label travels with circumstances rather than with the product. A second slip is reaching for cross-price elasticity to answer an income question. Cross-price elasticity separates substitutes from complements, and only income elasticity separates normal from inferior.
Normal Good questions
How do you tell whether a good is normal or inferior?
Income elasticity of demand answers it. Divide the percentage change in quantity demanded by the percentage change in income, holding prices constant. A positive result means the good is normal, because income and quantity move in the same direction. A negative result means the good is inferior, because buyers switch away from it as they earn more. Only the sign classifies, while the size just tells you how strongly demand responds.
Can the same good be normal for one person and inferior for another?
Normal and inferior are labels attached to a buyer and an income range, not fixed properties of a product. Canned soup may be normal for a student earning very little and inferior for a household that starts earning more and shifts to fresh ingredients. Textbook examples such as bus travel or store brand cereal are only typical cases, so an exam answer should tie the label to a stated income change.
Are luxury goods and normal goods the same thing?
Luxury goods are a subset of normal goods. Every normal good has a positive income elasticity, and economists split that group at a value of one. Income elasticity between zero and one marks a necessity, where spending rises more slowly than income. Income elasticity above one marks a luxury, where quantity demanded outpaces income growth. All luxuries are normal goods, but many normal goods are necessities rather than luxuries.
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Related terms
Common comparisons
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