The theory of supply and demand usually assumes that markets are perfectly competitive. This implies that there are many buyers and sellers in the market and none of them have the capacity to significantly influence prices of goods and services. In many real-life transactions, the assumption fails because some individual buyers or sellers have the ability to influence prices. Quite often, a sophisticated analysis is required to understand the demand-supply equation of a good model. However, the theory works well in situations meeting these assumptions.
Mainstream economics does not assume a priori that markets are preferable to other forms of social organization. In fact, much analysis is devoted to cases where so-called market failures lead to resource allocation that is suboptimal by some standard (defence spending is the classic example, profitable to all for use but not directly profitable for anyone to finance). In such cases, economists may attempt to find policies that will avoid waste, either directly by government control, indirectly by regulation that induces market participants to act in a manner consistent with optimal welfare, or by creating "missing markets" to enable efficient trading where none had previously existed. Market failure in positive economics (microeconomics) is limited in implications without mixing the belief of the economist and his or her theory.
The demand for various commodities by individuals is generally thought of as the outcome of a utility-maximizing process, with each individual trying to maximize their own utility. The interpretation of this relationship between price and quantity demanded of a given good assumes that, given all the other goods and constraints, the set of choices which emerges is that one which makes the consumer happiest.
Supply and Demand
Supply and demand is an economic model of price determination in a market. It concludes that in a competitive market, the unit price for a particular good will vary until it settles at a point where the quantity demanded by consumers (at current price) will equal the quantity supplied by producers (at current price), resulting in an economic equilibrium of price and quantity.
The four basic laws of supply and demand are:
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If demand increases and supply remains unchanged, then it leads to higher equilibrium price and higher quantity.
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If demand decreases and supply remains unchanged, then it leads to lower equilibrium price and lower quantity.
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If supply increases and demand remains unchanged, then it leads to lower equilibrium price and higher quantity.
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If supply decreases and demand remains unchanged, then it leads to higher equilibrium price and lower quantity.
Law of supply
The Law of Supply states that, (all other things unchanged) an increase in price results in an increase in quantity supplied. This means that producers are willing to offer more products for sale on the market at higher prices by increasing production as a way of increasing profits.
In economics, the law of demand is an economic law, which states that consumers buy more of a good when its price decreases and less when its price increases (ceteris paribus).
The greater the amount to be sold, the smaller the price at which it is offered must be, in order for it to find purchasers.
Law of demand states that the amount demanded of a commodity and its price are inversely related, other things remaining constant. That is, if the income of the consumer, prices of the related goods, and tastes and preferences of the consumer remain unchanged, the consumer’s demand for the good will move opposite to the movement in the price of the good.
Assumptions
Every law will have limitations or exceptions. While expressing the law of demand, the assumption is that other conditions of demand are unchanged. If they remain constant, the inverse relation may not hold well. In other words, it is assumed that the income and tastes of consumers and the prices of other commodities are constant. This law operates when the commodity’s price changes and all other prices and conditions do not change.
The main assumptions are:
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Habits, tastes and fashions remain constant.
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Money, income of the consumer does not change.
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Prices of other goods remain constant.
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The commodity in question has no substitute or is not in competition by other goods.
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The commodity is a normal good and has no prestige or status value.
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People do not expect changes in the price.
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Price is independent and demand is dependent.
Exceptions to the law of demand
Generally, the amount demanded of good increases with a decrease in price of the good and vice versa. In some cases, however, this may not be true. Such situations are explained below.
Initially discovered by Robert Giffen, economists disagree on the existence of Giffen goods in the market. A Giffen good describes an inferior good that as the price increases demand for the product increases. As an example, during the Irish Potato Famine of the 19th century, potatoes were considered a Giffen good. Potatoes were the largest staple in the Irish diet, so as the price rose it had a large impact on income. People responded by cutting out on luxury goods such as meat and vegetables, and instead bought more potatoes. Therefore, as the price of potatoes increased, so did the demand.
Commodities which are used as status symbols
Some expensive commodities like diamonds, air conditioned cars, etc., are used as status symbols to display one’s wealth. The more expensive these commodities become, the higher their value as a status symbol and hence, the greater the demand for them. The amount demanded of these commodities increase with an increase in their price and decrease with a decrease in their price. Also known as a Veblen good.
Expectation of change in the price of commodity
If a household expects the price of a commodity to increase, it may start purchasing a greater amount of the commodity even at the presently increased price. Similarly, if the household expects the price of the commodity to decrease, it may postpone its purchases. Thus, law of demand is violated in such cases. In this case, the demand curve does not slope down from left to right; instead it presents a backward slope from the top right to down left. This curve is known as an exceptional demand curve. Technically, this is not a violation of the law of demand, as it violates the ceteris paribus condition.
Law of demand and changes in demand
The law of demand states that, other things remaining same, the quantity demanded of a good increases when its price falls and vice-versa. Note that demand for goods changes as a consequence of changes in income, tastes etc. Hence, demand may expand or contract and increase or decrease. In this context, let us make a distinction between two different types of changes that affect quantity demanded, viz., expansion and contraction; and increase and decrease.
While stating the law of demand i.e., while treating price as the causative factor, the relevant terms are Expansion and Contraction in demand. When demand is changing due to a price change alone, we should not say increase or decrease but expansion or contraction. If one of the non-price determinants of demand, such as the prices of other goods, income, etc. change & thereby demand changes, the relevant terms are increase and decrease in demand.
Limitations:
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Change in taste or fashion.
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Change in income
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Change in other prices.
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Discovery of substitution.
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Anticipatory change in prices.
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Rare or distinction goods.
There are certain goods which do not follow this law. These include Veblen goods and Giffen goods.
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