市場的行為與干預

什麼是市場干預？

市場干預的形式和影響是什麼？

價格干預 價格上限 ，價格下限

數量干預

干預的影響 : 「剩餘」和「福利」的概念

均衡價格如何受需求面供給面因素的影響？

Supply, Demand, and Government Policies

In a free, unregulated market system, market forces establish equilibrium prices and exchange quantities.

While equilibrium conditions may be efficient, it may be true that not everyone is satisfied.

One of the roles of economists is to use their theories to assist in the development of policies.

How Price Ceilings Affect Market Outcomes

Two outcomes are possible when the government imposes a price ceiling:

The price ceiling is not binding ( 無約束力 ) if set above the equilibrium price.

The price ceiling is binding if set below the equilibrium price, leading to a shortage.

Figure 1 A Market with a Price Ceiling(a) A Price Ceiling That Is Not Binding

Quantity ofIce-Cream

Cones

0

Price ofIce-Cream

Cone

Equilibriumquantity

$4 Priceceiling

Equilibriumprice

Demand

Supply

3

100

The market clears at $3 and the price ceiling is ineffective.

Figure 1 A Market with a Price Ceiling(b) A Price Ceiling That Is Binding

Quantity ofIce-Cream

Cones

0

Price ofIce-Cream

Cone

Demand

Supply

2 PriceceilingShortage

75

Quantitysupplied

125

Quantitydemanded

Equilibriumprice

$3

How Price Ceilings Affect Market Outcomes

Effects of Price Ceilings

A binding price ceiling creates

Shortages because QD > QS.

•Example: Gasoline shortage of the 1970s

Nonprice rationing

•Examples: Long lines, discrimination by sellers

CASE STUDY: Lines at the Gas Pump

Economists blame government regulations that limited the price oil companies could charge for gasoline.

In 1973, OPEC raised the price of crude oil in world markets. Crude oil is the major input in gasoline, so the higher oil prices reduced the supply of gasoline.What was responsible for the long gas lines?

Figure 2 The Market for Gasoline with a Price Ceiling(a) The Price Ceiling on Gasoline Is Not Binding

Quantity ofGasoline

0

Price ofGasoline

1. Initially,the priceceilingis notbinding . . . Price ceiling

Demand

Supply, S1

P1

Q1

Figure 2 The Market for Gasoline with a Price Ceiling(b) The Price Ceiling on Gasoline Is Binding

Quantity ofGasoline

0

Price ofGasoline

Demand

S1

S2

Price ceiling

QS

4. . . . resultingin ashortage.

3. . . . the priceceiling becomesbinding . . .

2. . . . but whensupply falls . . .

P2

QD

P1

Q1

Price Restrictions

Price Ceilings

The maximum legal price that can be charged

Examples:

• Gasoline prices in the 1970s• Housing in New York City• Proposed restrictions on ATM fees

Price Floors

The minimum legal price that can be charged.

Examples:

• Minimum wage• Agricultural price supports

Full Economic Price

The dollar amount paid to a firm under a price ceiling, plus the nonpecuniary price.

PF = Pc + (PF - PC) PF = full economic price

PC = price ceiling

PF - PC = nonpecuniary price

An Example from the 1970s

Ceiling price of gasoline - $1

3 hours in line to buy 15 gallons of gasoline

Opportunity cost: $5/hr

Total value of time spent in line: 3 $5 = $15

Non-pecuniary price per gallon: $15/15=$1

Full economic price of a gallon of gasoline: $1+$1=2

Housing Markets and Rent Ceilings價格上限The 1906 earthquake in San Francisco left 200,000 people—more than half the city—homeless.

By the time the San Francisco Chronicle started publishing again, a month after the earthquake, there was not a single mention of a housing shortage.

The classified advertisements listed many more houses and flats for rent than the advertisements for houses and flats wanted.

How did the market achieve this outcome?

Housing Markets and Rent Ceilings

The Market Response to a Decrease in Supply

Figure 6.1 shows the San Francisco housing market before the earthquake.

The quantity of housing was 100,000 units and the rent was $16 a month at the intersection of D and SS.

Housing Markets and Rent Ceilings

The earthquake decreased the supply of housing and the supply curve shifted leftward to SSA.

The rent increased to $20 a month and the quantity decreased to 72,000 units.

Housing Markets and Rent Ceilings

Long-Run Adjustments

The long-run supply of housing is perfectly elastic at $16 a month.

With the rent above $16 a month, new houses and apartments are built.

Housing Markets and Rent Ceilings

供給的減少使租金上漲 , 吸引新的供給而新增加的供給使租金下降

The quantity of housing increases and the rent falls to the pre-earthquake levels (other things remaining the same).

Housing Markets and Rent Ceilings

A Regulated Housing Market

A price ceiling 價格上限 is a regulation that makes it illegal to charge a price higher than a specified level.

When a price ceiling is applied to a housing market it is called a rent ceiling. 房租上限

If the rent ceiling is set above the equilibrium rent, it has no effect. The market works as if there were no ceiling.

But if the rent ceiling is set below the equilibrium rent, it has powerful effects.

Housing Markets and Rent Ceilings

the effects of a rent ceiling that is set below the equilibrium rent.

The equilibrium rent is $20 a month.

A rent ceiling is set at $16 a month.

So the equilibrium rent is in the illegal region.

Housing Markets and Rent Ceilings

At the rent ceiling, the quantity of housing demanded exceeds the quantity supplied and there is a housing shortage.

價格上限造成供不應求（短缺）

Housing Markets and Rent Ceilings

With a housing shortage, people are willing to pay $24 a month.

Because the legal price cannot eliminate the shortage, other mechanisms operate:

search activity

搜尋行為 ( 與成本 ) 增加 black markets 黑市

Figure 3 Rent Control in the Short Run and in the Long Run(a) Rent Control in the Short Run

(supply and demand are inelastic)

Quantity ofApartments

0

Supply

Controlled rent

RentalPrice of

Apartment

Demand

Shortage

Figure 3 Rent Control in the Short Run and in the Long Run(b) Rent Control in the Long Run

(supply and demand are elastic)

0

RentalPrice of

Apartment

Quantity ofApartments

Demand

Supply

Controlled rent

Shortage

Housing Markets and Rent Ceilings

Search Activity

The time spent looking for someone with whom to do business is called search activity.

When a price is regulated and there is a shortage, search activity increases.

Search activity is costly and the opportunity cost of housing equals its rent (regulated) plus the opportunity cost of the search activity (unregulated).

Because the quantity of housing is less than the quantity in an unregulated market, the opportunity cost of housing exceeds the unregulated rent.

Housing Markets and Rent Ceilings

Black Markets

A black market is an illegal market that operates alongside a legal market in which a price ceiling or other restriction has been imposed.

A shortage of housing creates a black market in housing.

Illegal arrangements are made between renters and landlords at rents above the rent ceiling—and generally above what the rent would have been in an unregulated market.

Housing Markets and Rent Ceilings

Inefficiency of Rent Ceilings

A rent ceiling leads to an inefficient use of resources.

The quantity of rental housing is less than the efficient quantity and there is a deadweight loss, 無謂的損失

A rent ceiling is also, usually, unfair.

It does not generally benefit the poor.

Rather, it hurts the mobile newcomers and favors the less mobile, established residents.

Impact of a Price Floor

Price

Quantity

S

D

P*

Q* QSQd

Surplus

PF

Comparative Static Analysis

How do the equilibrium price and quantity change when a determinant of supply and/or demand change?

The Labor Market and the Minimum Wage

New, labor-saving technologies become available every year, which mainly replace low-skilled labor.

Does the persistent decrease in the demand for low-skilled labor depress the wage rates of these workers?

The immediate effect of these technological advances is a decrease in the demand for low-skilled labor, a fall in the wage rate, and a decrease in the quantity of labor supplied.

Figure 6.4 on the next slide illustrates this immediate effect.

The Labor Market and the Minimum Wage

A decrease in the demand for low-skilled labor is shown by a leftward shift of the demand curve.

A new labor market equilibrium arises at a lower wage rate and a smaller quantity of labor employed.

低技術勞工的需求減少 , 使均衡工資下降

The Labor Market and the Minimum Wage

In the long run, people get trained to do higher-skilled jobs.

The supply of low-skilled labor decreases, which is shown by a leftward shift of the short-run supply curve.

當勞工技能提昇 , 離開低階市場 , 供給減少 , 回到原來工資水準 例如 家事服務 居家看護

The Labor Market and the Minimum Wage

If long-run supply is perfectly elastic, the equilibrium wage rate returns to its initial level (other things remaining the same).

The Labor Market and the Minimum Wage

The Minimum Wage

A price floor 　價格下限 is a regulation that makes it illegal to trade at a price lower than a specified level.

When a price floor is applied to labor markets, it is called a minimum wage. 最低工資

If the minimum wage is set below the equilibrium wage rate, it has no effect. The market works as if there were no minimum wage.

If the minimum wage is set above the equilibrium wage rate, it has powerful effects.

The Labor Market and the Minimum Wage

If the minimum wage is set above the equilibrium wage rate, the quantity of labor supplied by workers exceeds the quantity demanded by employers. There is a surplus of labor.

Because employers cannot be forced to hire a greater quantity than they wish, the quantity of labor hired at the minimum wage is less than the quantity that would be hired in an unregulated labor market.

Because the legal wage rate cannot eliminate the surplus, the minimum wage creates unemployment

.

The Labor Market and the Minimum Wage

The equilibrium wage rate is $4 an hour.

The minimum wage rate is set at $5 an hour.

So the equilibrium wage rate is in the illegal region.

The Labor Market and the Minimum Wage

The quantity of labor employed is the quantity demanded.

The quantity of labor supplied exceeds the quantity demanded.

Unemployment 失業 is the gap between the quantity demanded and the quantity supplied.

The Labor Market and the Minimum Wage

The Minimum Wage in Practice

The United States has passed the Fair Standards Labor Act, which currently sets the minimum wage at $5.15 per hour.

This minimum wage has historically fluctuated between 35 percent and 50 percent of the average wage of production workers.

Most economists believe that minimum wage laws increase the unemployment rate of low-skilled younger workers. 最低工資反而可能增加低階勞工的失業

Consumer Surplus ( 消費者剩餘 ):

The value consumers get from a good but do not have to pay for.

I got a great deal!

That company offers a lot of bang for the buck!

Dell provides good value.

Total value greatly exceeds total amount paid.

Consumer surplus is large.

I got a lousy deal!

That car dealer drives a hard bargain!

I almost decided not to buy it!

They tried to squeeze the very last cent from me!

Total amount paid is close to total value.

Consumer surplus is low.

Price

Quantity

D

10

8

6

4

2

1 2 3 4 5

Consumer Surplus:The value received but notpaid for

Consumer Surplus: The Discrete Case

Consumer Surplus:The Continuous Case

Price $

Quantity

D

10

8

6

4

2

1 2 3 4 5

Valueof 4 units

Consumer Surplus

Total Cost of 4 units

Producer Surplus ( 生產者剩餘 ):

The amount producers receive in excess of the amount necessary to induce them to produce the good.

Price

Quantity

S0

Producer Surplus

Q*

P*

Market Equilibrium

Balancing supply and demand

QxS = Qx

d

Steady-state

均衡 (equilibrium)

一種不會自發性地改變的狀態

Taxes 稅

Who Pays a Sales Tax?

Demand and supply analysis shows how the buyer and the seller share the payment of a tax.

Buyers respond to the price with the tax, because that is the price they must pay.

Sellers respond to the price without the tax, because that is the price they receive.

The tax is a wedge between the price paid and price received, which changes the incentives faced by buyers and sellers.

Elasticity and Tax Incidence

What was the impact of tax?

Taxes discourage market activity.

When a good is taxed, the quantity sold is smaller.

Buyers and sellers share the tax burden.

Taxes

the effects of a sales tax on CD players.

The equilibrium price with no tax is $100.

A tax of $10 per CD player is introduced.

The curve S + tax shows the new supply curve.

Taxes

The vertical distance between the original supply curve and the supply curve with the tax is equal to the amount of the sales tax.

Buyers would have to pay $110 to induce firms to offer the original quantity for sale.

Taxes

The tax changes the equilibrium price and quantity.

The quantity decreases.

The price paid by the buyer rises to $105 and the price received by the seller falls to $95.

Taxes

The government collects a tax revenue on the decreased quantity.

The buyer and the seller share the tax payment.

In this example, they share it equally.

But it doesn’t always turn out that way.

Taxes

The division of the tax between the buyer and the seller depends on the elasticities of demand and supply.

Tax Division and Elasticity of Demand

To see the effect of the elasticity of demand on the division of the tax payment, we look at two extreme cases.

Perfectly inelastic demand: the buyer pays the entire tax.

Perfectly elastic demand: the seller pays the entire tax.

The more inelastic the demand, the larger is the buyers’ share of the tax.

Taxes

In this figure, demand is perfectly inelastic—the demand curve is vertical.

需求沒有彈性時 , 需求綫是垂直的 , 消費者負擔所有稅賦When a tax is imposed on this good, the buyer pays the entire tax.

Taxes

In this figure, demand is perfectly elastic—the demand curve is horizontal.

When a tax is imposed on this good, the seller pays the entire tax.

需求非常有彈性時 , 需求綫是水平的 , 供給者負擔所有稅賦

Taxes

Tax Division and Elasticity of Supply

To see the effect of the elasticity of supply on the division of the tax payment, we again look at two extreme cases.

Perfectly inelastic supply: the seller pays the entire tax.

Perfectly elastic supply: the buyer pays the entire tax.

The more elastic the supply, the larger is the buyers’ share of the tax.

Taxes

In this figure, supply is perfectly inelastic—the supply curve is vertical.

When a tax is imposed on this good, the seller pays the entire tax.

供給沒有彈性時 , 供給綫是垂直的 , 供給者負擔所有稅賦

Taxes

In this figure, supply is perfectly elastic—the supply curve is horizontal.

When a tax is imposed on this good, the buyer pays the entire tax.

供給非常有彈性時 , 供給綫是水平的 , 消費者負擔所有稅賦

Taxes

Sales Taxes in Practice

Taxes usually are levied on goods and services with an inelastic demand.

The quantity purchased does not decrease by much after the tax is imposed.

The government collects relatively larger tax receipts.

Taxes

Taxes and Efficiency

Except in the extreme cases of perfectly inelastic demand or supply when the quantity remains the same, imposing a tax creates inefficiency.

Figure 6.9 shows the inefficiency created by a $10 tax on CD players.

Taxes

With no tax, the market is efficient and the sum of consumer surplus and producer surplus is maximized.

A tax shifts the supply curve, decreases the equilibrium quantity, raises the price to the buyer, and lowers the price to the seller.

Taxes

The tax revenue takes part of the consumer surplus and producer surplus.

The decreased quantity creates a deadweight loss.

無謂的損失

Elasticity and Tax Incidence

In what proportions is the burden of the tax divided?

How do the effects of taxes on sellers compare to those levied on buyers?

The answers to these questions depend on the elasticity of demand and the elasticity of supply.

Figure 9 How the Burden of a Tax Is Divided

Quantity0

Price

Demand

Supply

Tax

Price sellersreceive

Price buyers pay

(a) Elastic Supply, Inelastic Demand

2. . . . theincidence of thetax falls moreheavily onconsumers . . .

1. When supply is more elasticthan demand . . .

Price without tax

3. . . . than on producers.

Figure 9 How the Burden of a Tax Is Divided

Quantity0

Price

Demand

Supply

Tax

Price sellersreceive

Price buyers pay

(b) Inelastic Supply, Elastic Demand

3. . . . than onconsumers.

1. When demand is more elasticthan supply . . .

Price without tax

2. . . . theincidence of the tax falls more heavily on producers . . .

勞委會的看護工政策

巴氏量表將不再是衡量聘雇外勞的唯一依據，未來將改由「醫療評估小組」來決定，只有被小組認定需要二十四小時照顧，同時找不到本國看護的病人，才能申請外籍監（看）護工。至於找尋本國看護的辦法，是根據勞委會訂定的二十四小時照護「每月合理薪資三萬元至三萬五千元」，招募本國籍看護。每雇用一名本國看護，政府每月發給雇主雇用獎助金五千元，最長補助一年。

如果是在北高等人口密集都會區，能夠擔任居住在家中，二十四小時照顧老病，且要處理相關飲食、洗滌、大小便的本國勞工，現在的行情是每天兩千元，每月六萬元，而且很難找到年紀比較輕、體力比較好、有能力負擔工作壓力的適當本勞。

本國勞工雇用數 外國勞工雇用數

P*=6每月工資

萬

元每月工資

萬

元

2.5

0.5 萬元

P’

Q* Q’Q’ Q*

Elasticity and Tax Incidence

So, how is the burden of the tax divided?

The burden of a tax falls more heavily on the side of the market that is less elastic.

Price controls include price ceilings and price floors.

A price ceiling is a legal maximum on the price of a good or service.

An example is rent control.

A price floor is a legal minimum on the price of a good or a service.

An example is the minimum wage.

Taxes are used to raise revenue for public purposes.

When the government levies a tax on a good, the equilibrium quantity of the good falls.

A tax on a good places a wedge between the price paid by buyers and the price received by sellers.

The incidence of a tax refers to who bears the burden of a tax.

The incidence of a tax does not depend on whether the tax is levied on buyers or sellers.

The incidence of the tax depends on the price elasticities of supply and demand.

The burden tends to fall on the side of the market that is less elastic.