DEMAND AND SUPPLY 3CHAPTER

需求與供給

Objectives

After studying this chapter, you will be able to:

Describe a competitive market and think about a price as an opportunity cost

Explain the influences on demand

Explain the influences on supply

Explain how demand and supply determine prices and quantities bought and sold

Use demand and supply to make predictions about changes in prices and quantities

目標目標

Slide, Rocket, Roller Coaster

Some prices slide, some rocket, and some roller coaster.

This chapter explains how prices are determined and how markets guide and coordinate choices.

溜滑梯 , 火箭 , 雲霄飛車

Markets and Prices

A market is any arrangement that enables buyers and sellers to get information and do business with each other.

A competitive market (競爭市場 )is a market that has many buyers and many sellers so no single buyer or seller can influence the price.

有很多的買方與賣方，所以沒有任何一個買方或賣方能影響價格。

The money price (貨幣價格 )of a good is the amount of money needed to buy it.

是指為了要取得財貨，必須要用多少貨幣單位以交換之

The relative price (相對價格 )of a good—the ratio of its money price to the money price of the next best alternative good—is its opportunity cost. 機會成本的概念

市場與價格

Demand

If you demand something, then you:

Want it, 想要 Can afford it, and 買得起 Have made a definite plan to buy it.已經計畫要買它

Wants are the unlimited desires or wishes people have for goods and services. Demand reflects a decision about which wants to satisfy.

The quantity demanded of a good or service is the amount that consumers plan to buy during a particular time period, and at a particular price.

需求

Demand

What Determines Buying Plans?

The amount of any particular good or service that consumers plan to buy is influenced by many factors.

1. The price of the good, 財貨的價格

需求

什麼決定購買計畫？

Demand

The Law of Demand 需求法則The law of demand states:

Other things remaining the same, the higher the price of a good, the smaller is the quantity demanded.其他條件不變下，財貨的價格愈高，需求量愈小

The law of demand results from

a substitution effect 替代效果

an income effect 所得效果

需求

Demand

Substitution effect 替代效果 — when the relative price (opportunity cost) of a good or service rises, people seek substitutes for it, so the quantity demanded decreases.

.

其他條件不變，當財貨價格變貴時，其相對價格或是機會成本也隨之上升，雖然每一種財貨都是獨一無二的，但仍有替代品 (substitute) ，則財貨的機會成本增加時，人們對該財貨的需求量會減少，而買比較多的替代品。

其他條件不變，當財貨價格變貴時，其相對價格或是機會成本也隨之上升，雖然每一種財貨都是獨一無二的，但仍有替代品 (substitute) ，則財貨的機會成本增加時，人們對該財貨的需求量會減少，而買比較多的替代品。

需求

Demand

Income effect 所得效果 — when the price of a good or service rises relative to income, people cannot afford all the things they previously bought, so the quantity demanded decreases其他因素不變，當財貨的價格增加時，相對於所得而言，價其他因素不變，當財貨的價格增加時，相對於所得而言，價格上升了，所以當財貨價格變貴而所得不改變時，人們沒有格上升了，所以當財貨價格變貴而所得不改變時，人們沒有辦法像以前一樣買得起所有的東西，必須至少減少某些財貨辦法像以前一樣買得起所有的東西，必須至少減少某些財貨的需求量，正常情況下，比較貴的財貨需求量將會減少。的需求量，正常情況下，比較貴的財貨需求量將會減少。

需求

Demand

Demand Curve and Demand Schedule

The term demand ( 需求 )refers to the entire relationship between the price of the good and quantity demanded ( 需求量 )of the good.

demand是指財貨價格與需求量間的整體關係

quantity demanded每個特定價格下所對應的需求量A demand curve ( 需求曲線 )shows the relationship between the quantity demanded of a good and its price when all other influences on consumers’ planned purchases remain the same.

需求

Demand

Figure 3.1 shows a demand curve for recordable compact discs (CD-Rs).

A rise in the price, other things remaining the same, brings a decrease in the quantity demanded and a movement along the demand curve.

需求

Demand

A demand curve is also a willingness-and-ability-to-pay curve.

The smaller the quantity available, the higher is the price that someone is willing to pay for another unit.

Willingness to pay measures marginal benefit.

需求

Demand

A Change in Demand

When any factor that influences buying plans other than the price of the good changes, there is a change in demand for that good. The quantity of the good that people plan to buy changes at each and every price, so there is a newnew demand demand curvecurve.

When demand increases, the quantity that people plan to buy increases at each and every price so the demand curve shifts rightward.

When demand decreases, the quantity that people plan to buy decreases at each and every price so the demand curve shifts leftward.

需求

Demand

The factors that change demand are:

1.The prices of related goods,其他相關財貨的價格

2. Expected future prices,預期未來的價格

3. Income,所得

4. Expected future income預期未來的所得

5. Population, and人口

6. Preferences.偏好

需求

Demand

Prices of related goods

A substitute (替代財 ) is a good that can be used in place of another good.

A complement (互補財 )is a good that is used in conjunction with another good.

When the price of substitute for CD-Rs rises or when the price of a complement for CD-Rs falls, the demand for CD-Rs increases.

需求

Demand

Figure 3.2 shows the shift in the demand curve for CD-Rs when the price of CD burner falls.

Because a CD burner is a complement of a CD-R, the demand for CD-Rs increases.

需求

Demand

Expected future prices預期未來的價格

If the price of a good is expected to rise in the future, current demand increases and the demand curve shifts rightward.

Income所得

When income increases, consumers buy more of most goods and the demand curve shifts rightward. A normal good (正常財 )is one for which demand increases as income increases. An inferior good (劣等財 )is a good for which demand decreases as income increases.

需求

Demand

Population 人口

The larger the population, the greater is the demand for all goods.

Preferences 偏好

People with the same income have different demands if they have different preferences.

需求

Demand

需求法則CD-R需求量

量將減少： 量將增加：

CD-R的價格上升 CD-R的價格下降

需求

Table 3.1 Summarize the demand for CD-Rs

Demand

需求變動對 CD-R需求的變動需求減少： 需求增加：

替代品的價格下降 替代品的價格上升

互補品的價格上升 互補品的價格下降

CD-R預期未來的價格下降 CD-R預期未來的價格上升

所得減少 所得增加

人口減少 人口增加

Table 3.1 Summarize the demand for CD-Rs

Demand

A Change in the Quantity Demanded Versus a Change in Demand

Figure 3.3 illustrates the distinction between a change in demand and a change in the quantity demanded.

需求

Demand

When the price of the good changes and everything else remains the same, there is a change in the quantity demanded and a movement along the demand curve.

沿著需求曲線上下點的移動

需求量變動 (change in the quantity demanded)

需求

Demand

When one of the other factors that influence buying plans changes, there is a change in demand and a shift of the demand curve.

需求變動 (change in demand)

需求曲線整條線的移動需求曲線整條線的移動

需求

Supply

If a firm supplies a good or service, then the firm:

Has the resources and the technology to produce it,

Can profit form producing it, and

Has made a definite plan to produce and sell it.

Resources and technology determine what it is possible to produce. Supply reflects a decision about which technologically feasible items to produce.

The quantity supplied (供給量 )of a good or service is the amount that producers plan to sell during a given time period at a particular price.在特定期間與特定的價格下，廠商願意生產及銷售的數量

供給 使用資源及技術以生產某種財貨，有限的資源及技術會限制生產

Supply

What Determines Selling Plans? 銷售計畫的決定因素 :

The amount of any particular good or service that a firm plans to supply is influenced by

1. The price of the good,

2. The prices of resources needed to produce it,

3. The prices of related goods produced,

4. Expected future prices,

5. The number of suppliers, and

6. Available technology.

供給

財貨的價格生產資源的價格

其他相關財貨的價格 預期未來的價格

供給者或廠商多寡技術

Supply

The Law of Supply

The law of supply states:

Other things remaining the same, the higher the price of a good, the greater is the quantity supplied.其他條件不變的情況下，財貨的價格愈高，供給量就愈多。

The law of supply results from the general tendency for the marginal cost of producing a good or service to increase as the quantity produced increases (Chapter 2, page 35).

Producers are willing to supply only if they at least cover their marginal cost of production.

供給

供給法則

供給量 (quantity supplied)在特定期間與特定的價格下，廠商願意生產及銷售的數量。

Supply

Supply Curve and Supply Schedule

The term supply ( 供給 )refers to the entire relationship between the quantity supplied and the price of a good.

The supply curve ( 供給曲線 ) shows the relationship between the quantity supplied of a good and its price when all other influences on producers’ planned sales remain the same.

供給

Supply

Figure 3.4 shows a supply curve of recordable compact discs (CD-Rs).

A rise in the price, other things remaining the same, brings an increase in the quantity supplied and a movement along the supply curve.

供給

Supply

A supply curve is also a minimum-supply-price curve.

The greater the quantity produced, the higher is the price that a firm must offered to be willing to produce that quantity.

供給曲線也可解釋為廠商在特定產量下 ,願意生產該產量所要求的最低價格曲線

供給

Supply

A Change in Supply

When any factor that influences selling plans other than the price of the good changes, there is a change in supply of that good. The quantity of the good that producers plan to sell changes at each and every price, so there is a new supply curve.

When supply increases, the quantity that producers plan to sell increases at each and every price so the supply curve shifts rightward.

When supply decreases, the quantity that producers plan to sell decreases at each and every price so the supply curve shifts leftward.

供給

供給變動

Supply

Table 3.2 (page 67) summarizes the factors that change supply. They are:

Prices of productive resources

If the price of resource used to produce a good rises, the minimum price that a supplier is willing to accept for producing each quantity of that good rises. So a rise in the price of productive resources decreases supply and shifts the supply curve leftward.( 左上移 )

供給

生產資源的價格

Supply

Prices of related goods produced

A substitute in production for a good is another good that can be produced using the same resources. Goods are compliments in production if they must be produced together.

註 : 量的方面 , 前者一增一減 , 後者同增同減

The supply of a good increases and its supply curve shifts rightward if the price of a substitute in production falls or if the price of a complement in production rises.

供給

其他相關財貨的價格變動

消費上的關係

生產上的關係

Supply

Expected future prices

If the price of a good is expected to fall in the future, current supply increases and the supply curve shifts rightward.

The number of suppliers

The larger the number of suppliers of a good, the greater is the supply of the good. An increase in the number of suppliers shifts the supply curve rightward.

供給

預期未來的價格

供給者多寡

Supply

Technology

Advances in technology create new products and lower the cost of producing existing products, so they increase supply and shift the supply curve rightward.

技術

供給

Supply

Figure 3.5 shows how an advance in the technology for producing CD-Rs increases the supply of CD-Rs and shifts the supply curve for CD-Rs rightward.

供給

Supply

A Change in the Quantity Supplied Versus a Change in Supply

Figure 3.6 illustrates the distinction between a change in supply ( 供給 ) and a change in the quantity supplied( 供給量 ).

供給

Supply

When the price of the good changes and other influences on selling plans remain the same, there is a change in the quantity supplied ( 供給量的變動 ). and a movement along the supply curve.

供給

Supply

When one of the other factors that influence selling plans changes, there is a change in supply ( 供給的變動 )and a shift of the supply curve.

供給

Table 3.2 Summary

供給法則CD-R供給量量將減少： 量將增加：CD-R價格下降 CD-R價格上升

供給變動CD-R供給供給減少： 供給增加：生產 CD-R使用的資源價格上升

生產 CD-R使用的資源價格下降

替代品價格上升 替代品價格下降互補品價格下降 互補品價格上升CD-R預期未來的價格上升

CD-R預期未來的價格下降

生產 CD-R廠商家數減少 生產 CD-R廠商家數增加

較差的生產技術 較好的生產技術

Market Equilibrium

Equilibrium is a situation in which opposing forces balance each other. Equilibrium in a market occurs when the price balances the plans of buyers and sellers.

簡言之 ,均衡為買賣雙方力量平衡的結果

The equilibrium price (均衡價格 ) is the price at which the quantity demanded equals the quantity supplied.供給量等於需求量的情況之下所得到的價格

The equilibrium quantity is the quantity bought and sold at the equilibrium price.買賣雙方在均衡價格之下所決定的數量

市場均衡

Price regulates buying and selling plans.Price regulates buying and selling plans.

Economics, 6th, Parkin, 2004, Chapter 3: 需求與供給 [ 第 42頁 ]

市場運作的結果都會朝均衡點移動，因為市場運作的結果都會朝均衡點移動，因為 價格會限制買賣雙方的計畫 價格會限制買賣雙方的計畫

當雙方計畫不配合時，價格會自動調整。 當雙方計畫不配合時，價格會自動調整。

Price adjusts when plans don’t match.

Market Equilibrium 市場均衡

Market Equilibrium

Price as a Regulator

Figure 3.7 illustrates the equilibrium price and equilibrium quantity in the market for CD-Rs.

If the price of a disc is $2, the quantity supplied exceeds the quantity demanded and there is a surplus ( 超額供給 ) of discs.

市場均衡

價格作為管制工具價格作為管制工具

Market Equilibrium

If the price of a disc is $1, the quantity demanded exceeds the quantity supplied and there is a shortage ( 供給短缺 )of discs.

If the price of a disc is $1.50, the quantity demanded equals the quantity supplied and there is neither a shortage nor a surplus of discs.

市場均衡

Market Equilibrium

Price Adjustments 價格調整At prices below the equilibrium, a shortage forces the price up.

短缺將促使價格上升At prices above the equilibrium, a surplus forces the price down.

生產過剩促使價格下降At the equilibrium price, buying plans selling plans agree and the price doesn’t change.

市場均衡

買賣雙方最好的交易狀況 : 均衡

Predicting Changes in Price and Quantity

Because the price rises if it is below equilibrium, falls if it is above equilibrium, and remains constant if it is at the equilibrium, the price is pulled toward the equilibrium and remains there until some event changes the equilibrium.

A change in price stems from a change in demand, a change in supply, or a change in both S and D.

預測價格與數量的變動

Predicting Changes in Price and Quantity

A Change in Demand

Figure 3.8 shows the effect of a change in demand.

An increase in demand shifts the demand curve rightward and creates a shortage at the original price.The price rises and the quantity supplied increases.

預測價格與數量的變動

Predicting Changes in Price and Quantity

A Change in Supply

Figure 3.9 shows the effect of a change in supply.

An increase in supply shifts the supply curve rightward and creates a surplus at the original price.

The price falls and the quantity demanded increases and quantity supplied decreases.

預測價格與數量的變動

Predicting Changes in Price and Quantity

A Change in Both Demand and Supply

A change both demand and supply changes the equilibrium price and the equilibrium quantity but we need to know the relative magnitudes of the changes to predict some of the consequences.

預測價格與數量的變動

Predicting Changes in Price and Quantity

Figure 3.10 shows the effects of a change in both demand and supply in the same direction. An increase in both demand and supply increases the equilibrium quantity but has an uncertain effect on the equilibrium price.

預測價格與數量的變動

Predicting Changes in Price and Quantity

Figure 3.11 shows the effects of a change in both demand and supply when they change in opposite directions. An increase in supply and a decrease in demand lowers the equilibrium price but has an uncertain effect on the equilibrium quantity.

預測價格與數量的變動

Economics, 6th, Parkin, 2004, Chapter 3: 需求與供給 [ 第 52頁 ]

均衡價格將下降均衡數量可能增加、減少、或維持不變均衡價格將下降均衡數量可能增加、減少、或維持不變

均衡價格將上升均衡數量可能增加、減少、或維持不變均衡價格將上升均衡數量可能增加、減少、或維持不變

1. 需求減少與供給增加同時發生1. 需求減少與供給增加同時發生

2. 需求增加與供給減少同時發生2. 需求增加與供給減少同時發生

3. 需求與供給同時增加

均衡價格均衡價格可能增加、減少、或維持不變可能增加、減少、或維持不變均衡數量將增加均衡數量將增加

3. 需求與供給同時增加

均衡價格均衡價格可能增加、減少、或維持不變可能增加、減少、或維持不變均衡數量將增加均衡數量將增加

3. 需求與供給同時減少

均衡價格均衡價格可能增加、減少、或維持不變可能增加、減少、或維持不變均衡數量將減少均衡數量將減少

3. 需求與供給同時減少

均衡價格均衡價格可能增加、減少、或維持不變可能增加、減少、或維持不變均衡數量將減少均衡數量將減少

THE END