Why does demand curve slope downward
The demand curve slopes downward from left to right, meaning as price decreases, quantity demanded increases, and as price increases, quantity demanded decreases. This happens because of several economic reasons.
1. Law of Diminishing Marginal Utility
MU = \frac{\Delta U}{\Delta Q}
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Marginal utility (MU) is the additional satisfaction from consuming one more unit of a product.
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As consumers consume more units, the additional satisfaction decreases.
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Therefore, consumers are only willing to buy additional units if the price falls.
Example:
The first slice of pizza gives high satisfaction, but the fifth slice gives less satisfaction. So consumers will only buy more slices if the price is lower.
2. Income Effect
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When the price of a product falls, the real purchasing power of consumers increases.
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Consumers feel richer and can buy more of the product.
Example:
If the price of rice falls, consumers can buy more rice with the same income.
3. Substitution Effect
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When the price of a good decreases, it becomes cheaper relative to substitutes.
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Consumers substitute the cheaper product for other goods.
Example:
If coffee becomes cheaper than tea, consumers may buy more coffee instead of tea.
4. New Consumers Enter the Market
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At higher prices, only a few consumers can afford the product.
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When the price decreases, more consumers are willing to buy it.
5. Multiple Uses of a Product
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Some goods have different uses.
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When the price is low, people use the product for additional purposes.
Example:
Electricity may be used only for lighting at high prices, but for heating, cooling, and other appliances when cheaper.
? Conclusion:
Because of diminishing marginal utility, income effect, substitution effect, entry of new buyers, and multiple uses, consumers demand more quantity at lower prices, which makes the demand curve slope downward.
