THE NEOCLASSICAL SCHOOL
--THE DEPARTURE FROM PURE COMPETITON
Qi Xin, Zhao Mengyue
Wang Fei, Duan Shuhong
ALVIN E. ROTH

a visiting professor at
Stanford University as well
as George Gund Professor
of Economics and Business
Administration (on leave) at
Harvard Business School.
He plans to take up a
permanent position at
Stanford at the beginning of
2013
ALVIN E. ROTH
He studies in the field of game theory, market
design and experimental economics, and is
known for his emphasis on applying his
economic theory to solutions for "real-world"
problems.
 He helped redesign mechanisms for selecting
medical residents, New York City high schools
and Boston primary schools.
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LLOYD SHAPLEY

He is a Professor
Emeritus at University of
California, Los Angeles,
affiliated with
departments of
Mathematics and
Economics.
LLOYD SHAPLEY
He studies in the field of mathematical
economics and especially game theory.
 Shapley value, stochastic games, the
Bondareva-Shapley theorem and so on.
 His early work with R.N.Snow and Samuel
Karlin on matrix games was so complete that
little has been added since.

JUST FOR FUN
有三个人在海难后流落到了荒岛，
这三人中有一位是物理学家，一位是化学家，
另外一位是经济学家。他们三人在研究如何打
开一个罐头充饥。物理学家说，我们将罐头抛
下山，利用地心吸力的原理，使得罐头加速下
坠而打开。化学家说，我们应该把太阳能当成
实验室的酒精灯，烧烤罐头让它产生化学变化
而打开。最后这位经济学家说我们假设这个
罐头是打开的。。。
PERFECTLY COMPETITIVE MARKET
ASSUMPTIONS

1. Infinite buyers and sellers
2. Zero entry and exit barriers
3. Perfect factor mobility
4. Perfect information
5. Zero transaction costs
6. Profit maximization
7. Homogenous products
8. Property rights
IMPERFECTLY COMPETITIVE MARKET
1. In reality: reasons
a. barriers for market entry
b. patents
c. technology
d. regulations
…
IMPERFECTLY COMPETITIVE MARKET
2. Forms
a. monopoly
b. oligopoly
c. monopolistic competition
d. monopsony: in which there is only one buyer of a good.
e. oligopsony: in which there are few buyers of a good.
f. Information asymmetry
IMPERFECTLY COMPETITIVE MARKET
3. Scholars
a. Piero Sraffa: criticize Marshall’s theory
b. Edward Hastings Chamberlin: heterogeneous
products
c. Joan Violet Robinson: monopsony
PIERO SRAFFA
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British Italian economist
Born in Turin, Italy, 1898.
His father is Professor in Commercial Law
University Foundation in Turin, and registered in the
Faculty of Law,
1917，be made to do conscription service
Due to Intensifying fascist rule, he emigrated to
Britain in 1927, becoming a Cambridge University
lecturer. Lecture on “History of value theory" and
"German and Italian banking system"
He has been Fellow of Trinity College, Cambridge
ACHIEVEMENTS
1925, Sraffa published the relationship between
cost and production
 1926, The Laws of Returns under Competitive
Conditions
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1951-1955, editor of Ricardo's works and
correspondence
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opened the door leading to the modern imperfect
competition theory.
taken as founding the Neo-Ricardian school
1960, Production of Commodities by Means of
Commodities

Revival of the classical school’s thinking
BEGINNING OF MODERN IMPERFECT COMPETITION
THEORY

Marshall's theories contradict with each other
 Supply
and demand curves to determine the price
and quantity
 perfect competition
perfect competition
free to expand production
Increasing returns to scale
diminishing cost / unnecessary to low its price
Expand production
damage perfect competition
perfect competition
horizontal demand curve
companies can sell any number of products at a certain price
horizontal marginal cost curve
In input market, companies can buy any number of input at a
certain price.
marginal revenue curve and marginal cost
curve does not have an intersection

There are the definition confusion in industrial
equilibrium theory of Marshall
Different assumptions
 Different application area

Heterogeneous products
 Consumers' loyalty
 producers will have a protected market. In this
part of the market, producer may have a
monopoly status: they will not lose the whole
market even if they raise price.

He highlighted the weaknesses of the perfectly
competitive model commonly used in
traditional economics.
 Sraffa cast light on imperfect competition
theory

EDWARD CHAMBERLIN
(1899～1967)
 born in Washington, DC
 professor at Harvard
University
 Theory of monopolistic competition
CHAMBERLIN'S THOUGHT

market is neither competitive, nor
monopolistic.

product is different.
THEORY OF MONOPOLISTIC COMPETITION

assumptions:

product differentiation
1.
Alternative forms of differentiation: quality differences;
additional service; location; and packaging.
2.
Results in firm facing a downward-sloping demand
curve.Demand curve is highly, but not perfectly, elastic.
THEORY OF MONOPOLISTIC COMPETITION

product group
The output of a set of firms constitute a product group if the
substitutability in demand among the products is very high
relative to the substitutability between those firms’outputs
and other goods generally.
THEORY OF MONOPOLISTIC COMPETITION

uniformity
all the firm faces the same demand curve and have the
same cost function.

many sellers.
Many firms competing for the same group of customers(顾
客群) or product group(产品组).
MONOPOLISTIC COMPETITION
ELASTIC DEMAND CURVE
similar to that of a monopolist,
but demand is flatter
DEMAND CURVE FACED BY MONOPOLISTIC
COMPETITION’S FIRM
D: Proportional Demand Curve（比例
需求曲线）（客观需求曲线）
d: Subjective Demand Curve (主观需求
曲线)
MONOPOLISTIC COMPETITOR -SHORT RUN
1. MR=MC and The two demand
curves intersect at the same point.
2. P≥SAVC
LONG-RUN OPERATION IN MONOPOLISTIC
COMPETITION
 Firm
Demand Shifts In and Gets More
Elastic.
 Demand Shifts Back Because More Firms Enter the
Industry, So There is Less Demand Per Firm.
 Demand Gets More Elastic Because More Firms
Means More Substitutes and More Substitutes Means
More Elastic.
LONG-RUN OPERATION IN MONOPOLISTIC
COMPETITION
 Firms will enter and exit until the firms are
making exactly zero economic profits.
 Two characteristics of monopolistic
competition in the long-run:

Price exceeds marginal cost

Price equals average total cost
LONG-RUN OPERATION IN MONOPOLISTIC
COMPETITION
MAIN CONTRIBUTION

They abandon traditional assumptions of new
classical economics with Marshall that perfect
competition as a universal and monopoly as individual
exceptions, they think perfect competition and
monopoly are two extreme situations, proposed
monopoly competition between the two extremes.
JOAN ROBINSON
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British, (1903-1983)
Neo Cambridge School(新剑桥学派）, a longtime professor at Cambridge University
the only woman who can be considered a great
economist
JOAN ROBINSON
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Born in 31 October 1903
Learn economics at Girton College, Cambridge，
Student of Marshal’s
Married economist Austin Robinson in 1926
Became a lecturer in economics at the University
of Cambridge in 1937
Full professor and fellow of Girton College in 1965.
First female fellow of King's College in 1979
MAJOR WORKS
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The Economics of Imperfect Competition (1933)
An Essay on Marxian Economics (1942)
Accumulation of Capital (1956)
Exercises in Economic Analysis (1960)
Essays in the Theory of Economic Growth (1962)
Economic Philosophy: An essay on the progress of economic
thought (1962)
Freedom and Necessity: An introduction to the study of
society (1970)
Economic Heresies: Some Old Fashioned Questions in
Economic Theory, (1971)
Contributions to Modern Economics, (1978)
THE ECONOMICS OF IMPERFECT COMPETITION

不完全竞争是现实市场中最为普遍的形式

边际收入和边际成本决定价格

厂商具有垄断力量 市场可分的 同一产品在不同市场中的需
求弹性不同 会有价格歧视

更关注买方市场而非卖方市场。提出了“买方垄断”
（monopsony）这个概念。
EQUILIBRIUM OF THE MONOPOLISTIC FIRM
要解决单个企业或垄断者的产量和价格决定问题
漠视平均总成本 注重直接边际成本
均衡条件：MR=MC
竞争均衡

(1)不完全竞争下的均衡：
企业处于个别均衡状态时可获得额外利润 条件：MR=MC
企业处于完全均衡状态时,企业没有额外利润
条件：MR=MC AR=AC
(2)完全竞争下的均衡：P=MC=MR
买方垄断MONOPSONY
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效用: 商品使买主感到值得拥有的那种性质
买方垄断者：单个买主
买主间的完全竞争： 1、任何一个买主的采购量变化对该
市场总采购量只会产生微不足道的影响 2、卖主对买主一视
同仁
In competition, price = MU
In monopsony, MC of buyer = MU
边际效用被定义为等于边际成本的某种数量
买方垄断MONOPSONY

当处于完全竞争市场条件下时，如果市场价格为4，消费者会
购买产品直到价格等于边际效用为止；当处于买方垄断的情
形时，买方要得到更多的产品，他就必须要相应地支付更高
的价格【因为面临向上倾斜的供给曲线】，此时买方就要考
虑边际成本和边际效用之间的大小，他会购买产品直到二者
相等为止。
买方垄断MONOPSONY
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结论：在买方垄断的情形下，由于面临向上倾斜的产品供给
曲线，买方垄断者购买的产品数量比完全竞争条件下要少，
支付的价格比完全竞争条件下要低。
其他情况：
1）水平的供给曲线。此时买方垄断情况将与完全竞争情况一
致。
2）向下倾斜的供给曲线。此时买方垄断者购买的产品数量会
较完全竞争时为多。
买方垄断MONOPSONY

例子：如果存在劳动力市场的买方垄断，那么厂商雇佣工人
的数量和支付的工资水平将会怎样？
买方垄断MONOPSONY
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均衡点在N点，因为此时厂商雇佣工人的边际收益正
好等于边际成本。此时对应的雇佣工人数量为A，工
资率为L。
结论：1）在买方垄断的劳动力市场中，与完全竞争
市场相比，厂商雇佣工人的数量更少、工资更低
【完全竞争市场的均衡点为S，对应的雇佣工人数量
为B，工资率为K】；2）工人受到剥削，因为其边际
收益产品对应的工资率为H，高于其实际工资L。
剥削
剥削：一批工人的工资低于他们的按售价计的边际实物产量
产生原因
：劳动供给或商品需求缺乏完全弹性
分类:
(1)对个别雇主的劳动供给是完全有弹性的时候。这是由于商
品的垄断而造成的.
(2)当劳动供给是不完全有弹性的时候(商品是在完全竞争的条
件下售出）
(3)当劳动供给是不完全有弹性的并且雇主在购买劳动时能实
行价格歧视
