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Normal good

Normal good is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Normal good rather than just read about it. In short: In economics, a normal good is a type of a good for which consumers increase their demand due to an increase in income, unlike inferior goods, for which the opposite is observed. When there is an increase in a person's income, for example due to a wage rise, a good for which the demand rises due to the wage increase, is referred as a normal good.

Normal good — main illustration
Normal good — illustration

Key takeaways

  • Normal good belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Normal good to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Normal good from memory before moving on to harder problems.

Reference excerpt

In economics, a normal good is a type of a good for which consumers increase their demand due to an increase in income, unlike inferior goods, for which the opposite is observed. When there is an increase in a person's income, for example due to a wage rise, a good for which the demand rises due to the wage increase, is referred as a normal good. Conversely, the demand for normal goods declines when the income decreases, for example due to a wage decrease or layoffs. Whether a good is categorized as a normal good or an inferior good is based on empirical observations, not some essential element of a good. Indeed, the same good may be a normal good for one group of consumers and an inferior good for another group. For example, for moderate-income consumers, a BMW 3 Series car might be a normal good, but for an upper-income group, it might be an inferior good.

Analysis There is a positive correlation between the income and demand for normal goods, that is, the changes income and demand for normal goods moves in the same direction. That is to say, that normal goods have an elastic relationship for the demand of a good with the income of the person consuming the good. In economics, the concept of elasticity, and specifically income elasticity of demand is key to explain the concept of normal goods. Income elasticity of demand measures the magnitude of the change in demand for a good in response to a change in consumer income. the income elasticity of demand is calculated using the following formula, Income elasticity of demand= % change in quantity demanded / % change in consumer income. In mathematical terms, the formula can be written as follows:

ξ i = Δ Q / Q Δ Y / Y {\displaystyle \xi _{i}={\frac {\Delta Q_{/}Q}{\Delta Y/Y}}} , where Q {\displaystyle Q} is the original quantity demanded and Y {\displaystyle Y} is the original income, before any change. A good is classified as a normal good when the income elasticity of demand is greater than zero and has a value less than one. If we look into a simple hypothetical example, the demand for apples increases by 10% for a 30% increase in income, then the income elasticity for apples would be 0.33 and hence apples are considered to be a normal good.

Comparison with luxury goods Other types of goods like luxury goods and necessities are also classified using the income elasticity of demand. The income elasticity of demand for luxury goods is greater than one, while for necessities it is less than one. Luxury goods have a positive correlation of demand and income, but a greater proportion of income is spent on a luxury item, for example, a sports car. On the other hand, with necessities or normal goods, people spend a smaller proportion of their income. Practically, a higher-income group of people spend more on luxury items and a lower-income group of people spend more of their income on necessities or normal goods. However, the classification of normal and luxury goods vary from person to person. A good that is considered to be a normal good to a lot of people may be considered to be luxury good to someone else. This depends on a lot of factors such as geographical locations, socio-economic conditions in a country, local traditions and many more. For example, in the 1980s in the Soviet Union, regular consumer items imported from the United States, such as Levis blue jeans and popular music cassettes, were costly, rare luxury goods.

Normal goods and consumer behaviour The demand for normal goods are determined by many types of consumer behaviour. A rise in income leads to a change in consumer behaviour. When income increases, consumers are able to afford goods that they could not consume before an income rise. The purchasing power of consumers increases. In this situation, the demand rises because of the attractiveness to consumers. The goods are attractive to the consumers maybe because they are high in quality and functionality and also the goods may help to maintain a certain socio economic prestige. Individual consumers have unique behavioural characteristics and they have their preferences accordingly. According to economic theory, there must be at least one normal good in any given bundle of goods (i.e. not all goods can be inferior). Economic theory assumes that a good always provides marginal utility (holding everything else equal). Therefore, if consumption of all goods decrease when income increases, the resulting consumption combination would fall short of the new budget constraint frontier. This would violate the economic rationality assumption. When the price of a normal good is zero, the demand is infinite.

Examples

… excerpt ends here. Continue reading the full article.

Illustrations

Normal good: Example of a normal good: As income increases from B1 to B3, the outward movement of utility curve I dictates that the quantity of good X1 increases in tandem. Therefore, X1 is a normal good. Put another way, the positively sloped income consumption curve demonstrates that X1 is normal. The Engel curve of X1 would also be positively sloped.
Example of a normal good: As income increases from B1 to B3, the outward movement of utility curve I dictates that the quantity of good X1 increases in tandem. Therefore, X1 is a normal good. Put another way, the positively sloped income consumption curve demonstrates that X1 is normal. The Engel curve of X1 would also be positively sloped.
Normal good: The graph shows the change in demand for both normal goods and luxury goods due to a change in income. When the income rises from 500 to 700, the quantity demanded for normal goods rises from 800 to 900.
The graph shows the change in demand for both normal goods and luxury goods due to a change in income. When the income rises from 500 to 700, the quantity demanded for normal goods rises from 800 to 900.
Normal good: Engels curves showing income elasticity of demand (YED) of normal goods (comprising luxury (red) and necessity goods (yellow)), perfectly inelastic (green) and inferior goods (blue)
Engels curves showing income elasticity of demand (YED) of normal goods (comprising luxury (red) and necessity goods (yellow)), perfectly inelastic (green) and inferior goods (blue)

Worked examples

Example 1 — a first encounter with Normal good

Start with the simplest possible case. Write down what Normal good claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Normal good before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Normal good ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Normal good

In research
Normal good appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Normal good in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Normal good is common in secondary-school and first-year university syllabi. It links to neighbouring topics Goods, so understanding it makes those chapters shorter.
In everyday life
Look for Normal good outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Normal good in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Normal good means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Normal good out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Normal good in simple terms?

In economics, a normal good is a type of a good for which consumers increase their demand due to an increase in income, unlike inferior goods, for which the opposite is observed. When there is an increase in a person's income, for example due to a wage rise, a good for which the demand rises due to…

Why does Normal good matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Normal good?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Normal good.

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