notes on chapter 4 of economics book by mankiw. graphs are taken from the same. topics covered WHAT IS MARKET? WHAT DETERMINES THE QUANTITY AN INDIVIDUAL DEMANDS? THE DEMAND SCHEDULE AND THE DEMAND CURVE MARKET DEMAND VERSUS INDIVIDUAL DEMAND SHIFTS IN THE DEMAND CURVE WHAT DETERMINES THE QUANTITY AN INDIVIDUAL SUPPLIES? THE SUPPLY SCHEDULE AND THE SUPPLY CURVE MARKET SUPPLY VERSUS INDIVIDUAL SUPPLY SHIFTS IN THE SUPPLY CURVE SUPPLY AND DEMAND TOGETHER THREE STEPS TO ANALYZING CHANGES IN EQUILIBRIUM

1. THE MARKET FORCES OF DEMAND AND SUPPLY
By
RAHUL SINHA

2. TOPICS COVERED
•WHAT IS MARKET?
• WHAT DETERMINES THE QUANTITY AN INDIVIDUAL DEMANDS?
•THE DEMAND SCHEDULE AND THE DEMAND CURVE
•MARKET DEMAND VERSUS INDIVIDUAL DEMAND
•SHIFTS IN THE DEMAND CURVE
•WHAT DETERMINES THE QUANTITY AN INDIVIDUAL SUPPLIES?
•THE SUPPLY SCHEDULE AND THE SUPPLY CURVE
•MARKET SUPPLY VERSUS INDIVIDUAL SUPPLY
•SHIFTS IN THE SUPPLY CURVE
•SUPPLY AND DEMAND TOGETHER
•THREE STEPS TO ANALYZING CHANGES IN EQUILIBRIUM

3. • A market is a group of buyers and sellers of a particular good or service. The buyers as a group determine the demand for the product, and the sellers as a group determine the supply of the product.
• For example, consider the market for ice cream in a particular town. Each buyer knows that there are several sellers from which to choose, and each seller is aware that his product is similar to that offered by other sellers. The price of ice cream and the quantity of ice cream sold are not determined by any single buyer or seller. Rather, price and quantity are determined by all buyers and sellers as they interact in the marketplace. This is called a competitive market.
WHAT IS MARKET?

4. WHAT DETERMINES THE QUANTITY AN INDIVIDUAL DEMANDS?
PRICE
•Law of demand – keeping other factors equal, law claims that the quantity demanded of a good is decreased if its price is increased and vice – versa.
INCOME
•Income of buyers also affects the demand of the good. If buyers have good income then quantity demanded is increased and vice-versa .
•If the demand for a good falls when income falls, the good is called a normal good. And if demand of a good rises by the decrease in income then the good is called inferior goods.
•An example of an inferior good might be bus rides. As your income falls, you are less likely to buy a car or take a cab, and more likely to ride the bus.

5. PRICES OF RELATED GOODS
•Sometimes a price of good is also affected by other goods that can be used in their place. For example if price of yogurt goes down then according to law of demand we will buy more yogurts instead of ice- cream.
•Two goods for which an increase in the price of one leads to an increase in the demand for the other are called substitute. Example - hot dogs and hamburgers.
•Two goods for which an increase in the price of one leads to a decrease in the demand for the other are called complements. Example - Gasoline and automobiles, computers and software.

6. TASTE
•Demand is also dependent on the taste of a buyer which is further dependent on historical and psychological factors of a buyer. Example – if in a place buyers like ice-creams the demand of ice-cream in that place will increase.
EXPECTATION
•Buyers expectations about the future may affect the demand for a good or service today.
•If buyers expect that price of a good will fall tomorrow then they will be unwilling to buy that good at present price.

7. THE DEMAND SCHEDULE AND THE DEMAND CURVE
•A table that shows the relationship between the price of a good and the quantity demanded is called demand schedule.
•A graph of the relationship between the price of a good and the quantity demanded is called demand curve.

9. MARKET DEMAND VERSUS INDIVIDUAL DEMAND
•The market demand is the sum of the individual demands. Because market demand is derived from individual demands, it depends on all those factors that determine the demand of individual buyers. Thus, market demand depends on buyers’ incomes, tastes, expectations, and the prices of related goods. It also depends on the number of buyers.

10. SHIFTS IN THE DEMAND CURVE
•Any change that increase the quantity demanded at every price will shift the curve towards right. And any change that decrease the quantity demanded at every price will shift the curve towards left.

11. For example-Suppose that the American Medical Association suddenly announces a new discovery: People who regularly eat ice cream live longer, healthier lives. Then this discovery will change people’s tastes and will raise the demand for ice cream. At any given price, buyers will now want to purchase a larger quantity of ice cream, and the demand curve for ice cream shifts to the right.

12. WHAT DETERMINES THE QUANTITY AN INDIVIDUAL SUPPLIES?
PRICE
•Law of supply –It claims that, keeping other things constant, the quantity of goods supplied is positively related to price of that good in the market, that is if the price of the good is high in the market the supply will be more and vice-versa.
INPUT PRICES
•The supply of a good is negatively related to the price of the inputs used to make the good.
•For example – a ice cream selling shop. The inputs are cream, sugar, flavouring, ice-cream machines and labours used. When the price of one or more inputs increase then there will be less profit and as a result the supply will decrease.

13. TECHNOLOGY
•This is also an important determinant for supply.
•New technology can decrease the input prices spent on labours used. Hence supply can be increased.
EXPECTATIONS
•If a seller expects that the price of the good will in increase in the future then he will keep some of his production in storage and this will decrease the supply in the market.

14. THE SUPPLY SCHEDULE AND THE SUPPLY CURVE
•A table that shows the relationship between the price of a good and the quantity supplied is called supply schedule.
•A graph of the relationship between the price of a good and the quantity supplied is called supply graph.

16. MARKET SUPPLY VERSUS INDIVIDUAL SUPPLY
•Market supply is the sum of the supplies of all sellers.
•Market supply depends on all those factors that influence the supply of individual sellers, such as the prices of inputs used to produce the good, the available technology, and expectations. In addition, the supply in a market depends on the number of sellers.

17. SHIFTS IN THE SUPPLY CURVE
•Any change that raises quantity supplied at every price shifts the supply curve to the right. Similarly, any change that reduces the quantity supplied at every price shifts the supply curve to the left.

19. SUPPLY AND DEMAND TOGETHER
•The price that balances supply and demand is called equilibrium price. At the equilibrium price, the quantity of the good that buyers are willing and able to buy exactly balances the quantity that sellers are willing and able to sell. The equilibrium price is sometimes called the market-clearing price because, at this price, everyone in the market has been satisfied: Buyers have bought all they want to buy, and sellers have sold all they want to sell.

21. THREE STEPS TO ANALYZING CHANGES IN EQUILIBRIUM
•We decide whether the event shifts the supply curve, the demand curve, or in some cases both curves.
•We decide whether the curve shifts to the right or to the left.
•We use the supply-and-demand diagram to examine how the shift affects the equilibrium price and quantity.

22. Example 1: A Change in Demand
Suppose that one summer the weather is very hot. This will affect the ice cream market in the following ways-
•The supply curve is unchanged because the weather does not directly affect the firms that sell ice cream. But due to increased demand the demand curve shifts.
• Because of the hot weather, people will start eating more ice-creams. Hence the demand of the ice-cream increased. As a consequence demand curve shifted from D1 to D2.
• As a result of increase in the demand the equilibrium price & equilibrium quantity increased.

24. Example 2: A Change in Supply
Suppose that, during another summer, an earthquake destroys several ice-cream factories. This will affect the ice-cream industry in the following ways.
•The earthquake affects the supply curve. By reducing the number of sellers, the earthquake changes the amount of ice cream that firms produce. So the supply curve shifts. The demand curve is unchanged because the earthquake does not directly change the amount of ice cream households wish to buy.
•The supply curve shifts to the left because, at every price, the total amount that firms are willing and able to sell is reduced. So the supply curve shifts from S1 to S2.
• As a result of earthquake, the equilibrium price increase and demand decreased.

26. Example 3: A Change in Both Supply and Demand
Suppose that the hot weather and the earthquake occur at the same time. This will affect the ice-cream market in the following ways.
•Due to the hot weather the demand curve will shift as people will start eating more ice-creams.
•Due to the earthquake, there will be decrease in the supply. So the supply curve will also shift.
• As the demand of ice-cream has increased so its curve will shift to right. And due to the decrease in the supply the supply curve will shift to left.
• In both cases, the equilibrium price rises. In panel
(a) Where demand increases substantially while supply falls just a little, the equilibrium quantity also rises.
(b) By contrast, where supply falls substantially while demand rises just a little, the equilibrium quantity falls.
•Thus, these events certainly raise the price of ice cream, but their impact on the amount of ice cream sold is ambiguous.

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