between competition and monopoly

9

Between Competition and Monopoly

● Monopolistic Competition

● Oligopoly

● Monopolistic Competition, Oligopoly, and Public Welfare

● A Glance Backward: Comparing the Four Market Forms

● Monopolistic Competition

● Oligopoly

● Monopolistic Competition, Oligopoly, and Public Welfare

● A Glance Backward: Comparing the Four Market Forms

OutlineOutline

Copyright© 2006 Southwestern/Thomson Learning All rights reserved.

Three Real World PuzzlesThree Real World Puzzles

1. Why are there so many retailers? ● E.g., intersections with 4 gas stations which is more than #

of cars warrants. Why and how do they all stay open?

2. Why do oligopolists advertise more than competitive firms?

● E.g., many big Co. use ads to battle for customers and ad budgets account for a huge portion of TC. Vs. farmers where few if any farms spend $ on ads.

3. Why do oligopolists seem to ∆P so infrequently?● E.g., ∆P commodities hourly but ∆P cars or refrigerators

only a few times a year.

1. Why are there so many retailers? ● E.g., intersections with 4 gas stations which is more than #

of cars warrants. Why and how do they all stay open?

2. Why do oligopolists advertise more than competitive firms?

● E.g., many big Co. use ads to battle for customers and ad budgets account for a huge portion of TC. Vs. farmers where few if any farms spend $ on ads.

3. Why do oligopolists seem to ∆P so infrequently?● E.g., ∆P commodities hourly but ∆P cars or refrigerators

only a few times a year.


Characteristics of Monopolistic CompetitionCharacteristics of Monopolistic Competition

1. Many small buyers and sellers

2. Freedom of entry and exit

3. Perfect information

4. Heterogeneous products: each seller’s product differs somewhat from every other seller’s product.

♦ E.g., Diff. in packaging, services, or consumers’ perceptions.

♦ Only characteristic that differs from perfect competition.

1. Many small buyers and sellers

2. Freedom of entry and exit

3. Perfect information

4. Heterogeneous products: each seller’s product differs somewhat from every other seller’s product.

♦ E.g., Diff. in packaging, services, or consumers’ perceptions.

♦ Only characteristic that differs from perfect competition.


Monopolistic CompetitionMonopolistic Competition

● D curve facing firm has (-) slope. ♦ Each seller’s product is different –they are not perfect

substitutes.

♦ ↑P will drive away some but not all of firm’s customers. Or ↓P will attract some but not all customers from rival firms.

● Freedom of entry and exit → firms cannot earn econ Π in LR. ♦ SR Π > 0 → new firms enter and ↓P until P = AC.

● Most U.S. firms are in this market structure.

● D curve facing firm has (-) slope. ♦ Each seller’s product is different –they are not perfect

substitutes.

♦ ↑P will drive away some but not all of firm’s customers. Or ↓P will attract some but not all customers from rival firms.

● Freedom of entry and exit → firms cannot earn econ Π in LR. ♦ SR Π > 0 → new firms enter and ↓P until P = AC.

● Most U.S. firms are in this market structure.


Determination of Price and Output under Monopolistic CompetitionDetermination of Price and Output under Monopolistic Competition

● Recall when D has (-) slope → P > MR.● Profit-max Q is where MR = MC.● Analysis looks like pure monopoly, but monop. comp.

firm (with rivals producing close substitutes) has a much flatter D curve.

● LR: Π = 0 → each firm produces where P = AC. So firm’s D curve must be tangent to its AC curve.

● Zero econ. Π in LR is seen in real world. ♦ E.g., Gas station owners do not earn higher Π than small

farmers under perfect competition.

● Recall when D has (-) slope → P > MR.● Profit-max Q is where MR = MC.● Analysis looks like pure monopoly, but monop. comp.

firm (with rivals producing close substitutes) has a much flatter D curve.

● LR: Π = 0 → each firm produces where P = AC. So firm’s D curve must be tangent to its AC curve.

● Zero econ. Π in LR is seen in real world. ♦ E.g., Gas station owners do not earn higher Π than small

farmers under perfect competition.

FIGURE 1. Short-Run Equilibrium Under Monopolistic Competition

FIGURE 1. Short-Run Equilibrium Under Monopolistic Competition

D

AC

P

3.40

Pri

ce p

er G

allo

n

Gallons of Gasoline per Week

12,000

$3.50

MR

MC

E

C

$3.80

$3.00

Π-max Q =12,000 and P = $3.50

Per unit Π = $0.10 → total Π = $1,200.

FIGURE 2. Long-Run Equilibrium Under Monopolistic Competition

FIGURE 2. Long-Run Equilibrium Under Monopolistic Competition

15,000

$3.35

Pri

ce p

er G

allo

n

Gallons of Gasoline per Week

10,000

$3.45

MR

MC

AC

D

E

P M

SR profits in Fig. 1 → new firms enter which shifts each firm’s D curve down until P = AC.

Compared with SR profits in Fig. 1:

a. P is lower in LR

b. more firms in industry; each produces a smaller Q with higher AC.


The Excess Capacity TheoremThe Excess Capacity Theorem

● In Fig. 2, AC at LR Q of firm (pt P) > min AC (pt M).● Pt M is where LR Q of a perf. comp. firm would be.● In LR, monop. comp. firm is producing where ↓AC but

has not yet reached its min.● Monopolistic competition leads to firms that have

unused or wasted capacity.● Resolve puzzle 1 –abundance of retailers: intersection

with 4 gas stations where 2 would suffice and operate at lower AC is real world ex. of excess capacity.

● In Fig. 2, AC at LR Q of firm (pt P) > min AC (pt M).● Pt M is where LR Q of a perf. comp. firm would be.● In LR, monop. comp. firm is producing where ↓AC but

has not yet reached its min.● Monopolistic competition leads to firms that have

unused or wasted capacity.● Resolve puzzle 1 –abundance of retailers: intersection

with 4 gas stations where 2 would suffice and operate at lower AC is real world ex. of excess capacity.


The Excess Capacity TheoremThe Excess Capacity Theorem

● Fewer firms in a monop. comp. market → each firm could ↑Q and ↓AC.

● Yet, fewer firms with larger quantities means there is less variety of product.

● Greater efficiency would be achieved at the cost of greater standardization.

● Not clear society would be better off with fewer firms.

● Fewer firms in a monop. comp. market → each firm could ↑Q and ↓AC.

● Yet, fewer firms with larger quantities means there is less variety of product.

● Greater efficiency would be achieved at the cost of greater standardization.

● Not clear society would be better off with fewer firms.


Oligopoly DefinedOligopoly Defined

● Oligopoly = market dominated by a few sellers, where several are large enough to affect market P.

● Great rivalry among firms with new product intros, free samples, and agro marketing campaigns.

● Degree of product differentiation varies by industry: none in steel plates but lots in cars.

● Some industries also contain large # of smaller firms (e.g., soft drinks) but they are dominated by a few large firms that get bulk of industry sales.

● Oligopoly = market dominated by a few sellers, where several are large enough to affect market P.

● Great rivalry among firms with new product intros, free samples, and agro marketing campaigns.

● Degree of product differentiation varies by industry: none in steel plates but lots in cars.

● Some industries also contain large # of smaller firms (e.g., soft drinks) but they are dominated by a few large firms that get bulk of industry sales.



● Firms strive to create unique products (in terms of features, location, or appeal) to shield themselves from competition that ↓P and ↓sales.

● More intense competition than pure competition. ♦ E.g., A corn farmer doesn’t make tough P decisions. He

accepts market P and reacts by picking Q.

♦ A farmer doesn’t need to advertise. He can sell as much as he likes at current market P.

♦ A farmer doesn’t worry about P policies his rivals are planning.

● Firms strive to create unique products (in terms of features, location, or appeal) to shield themselves from competition that ↓P and ↓sales.

● More intense competition than pure competition. ♦ E.g., A corn farmer doesn’t make tough P decisions. He

accepts market P and reacts by picking Q.

♦ A farmer doesn’t need to advertise. He can sell as much as he likes at current market P.

♦ A farmer doesn’t worry about P policies his rivals are planning.



● Oligopolists have some influence over market P, so they must consider rivals’ P; spend a fortune on ads; and try to predict their rivals’ actions.

● Resolve puzzle 2 –why oligopolists advertise and perfectly competitive firms do not.

1. Comp. firms can sell as much as they want at current P, so why advertise? Vs. Toyota faces a (-) sloped D curve, so it must ↓P or ↑ads (try to shift D out) to sell more cars.

2. Products are identical, so farm A’s ads might ↑ sales of farm B. Vs. Toyota’s ads may ↑ its sales and ↓ sales of rival carmakers.

● Oligopolists have some influence over market P, so they must consider rivals’ P; spend a fortune on ads; and try to predict their rivals’ actions.

● Resolve puzzle 2 –why oligopolists advertise and perfectly competitive firms do not.

1. Comp. firms can sell as much as they want at current P, so why advertise? Vs. Toyota faces a (-) sloped D curve, so it must ↓P or ↑ads (try to shift D out) to sell more cars.

2. Products are identical, so farm A’s ads might ↑ sales of farm B. Vs. Toyota’s ads may ↑ its sales and ↓ sales of rival carmakers.


Why Oligopolistic Behavior is So Difficult to AnalyzeWhy Oligopolistic Behavior is So Difficult to Analyze

● Largest firms can impact P and all firms must watch rivals’ actions.

● Analysis is difficult as firms’ decisions are inter-dependent and oligopolists know that outcomes of their decisions depend on rivals’ responses.♦ E.g., Toyota’s managers know that their actions will cause

reactions by Honda which may require Toyota to adjust its plans.

● Oligopolies have a variety of behavior patterns which requires different models to understand their behavior.

● Largest firms can impact P and all firms must watch rivals’ actions.

● Analysis is difficult as firms’ decisions are inter-dependent and oligopolists know that outcomes of their decisions depend on rivals’ responses.♦ E.g., Toyota’s managers know that their actions will cause

reactions by Honda which may require Toyota to adjust its plans.

● Oligopolies have a variety of behavior patterns which requires different models to understand their behavior.


Models of OligopolyModels of Oligopoly

● Different models to understand Oligopoly behavior:♦ Ignore interdependence

♦ Strategic interaction

♦ Cartels

♦ Price leadership and tacit collusion

♦ Sales maximization

♦ Kinked demand curve

♦ Game theory

● Different models to understand Oligopoly behavior:♦ Ignore interdependence

♦ Strategic interaction

♦ Cartels

♦ Price leadership and tacit collusion

♦ Sales maximization

♦ Kinked demand curve

♦ Game theory


Ignoring Interdependence Ignoring Interdependence

● Simplest model● Firms behave as if their actions will not spark reactions

from rivals.● Each firm seeks to max profits and assumes its P-Q

decision will not affect its rivals’ strategy.● Analyze oligopoly in the same way as pure monopoly.● This doesn’t explain most oligopoly behavior!

● Simplest model● Firms behave as if their actions will not spark reactions

from rivals.● Each firm seeks to max profits and assumes its P-Q

decision will not affect its rivals’ strategy.● Analyze oligopoly in the same way as pure monopoly.● This doesn’t explain most oligopoly behavior!


Strategic InteractionStrategic Interaction

● Consider 2 soap makers: X and Y.● X ↓P to $4.05 and assumes Y will continue its P = $4.12● Say Qx = 5m and X spends $1m on ads.● X may be surprised when Y cuts P to $4.00; ↑Qy to 8m

and sponsors the Super Bowl.● This ↓Πx and X wishes it didn’t cut P in first place.● X cannot afford to ignore how Y will react.

● Consider 2 soap makers: X and Y.● X ↓P to $4.05 and assumes Y will continue its P = $4.12● Say Qx = 5m and X spends $1m on ads.● X may be surprised when Y cuts P to $4.00; ↑Qy to 8m

and sponsors the Super Bowl.● This ↓Πx and X wishes it didn’t cut P in first place.● X cannot afford to ignore how Y will react.


CartelsCartels

● All firms agree to set P and Q → act as pure monopolist.● OPEC began making joint decisions in 1970’s and has

been successful over time at ↓Q oil and ↑P oil.● Cartels are difficult to organize and hard to enforce.

♦ Each member must produce small Q assigned by group. But once high P is established, every firm is tempted to cheat by ↑Qs. When cheating is suspected, cartel quickly falls apart as others ↑Qs which ↓P.

● Considered worse than monopoly. Cartel charges monopoly P without the cost savings from large scale production.

● All firms agree to set P and Q → act as pure monopolist.● OPEC began making joint decisions in 1970’s and has

been successful over time at ↓Q oil and ↑P oil.● Cartels are difficult to organize and hard to enforce.

♦ Each member must produce small Q assigned by group. But once high P is established, every firm is tempted to cheat by ↑Qs. When cheating is suspected, cartel quickly falls apart as others ↑Qs which ↓P.

● Considered worse than monopoly. Cartel charges monopoly P without the cost savings from large scale production.


Price Leadership and Tacit CollusionPrice Leadership and Tacit Collusion

● Overt collusion (where firms meet to pick P-Q) is illegal in the U.S. and rare. But tacit collusion is common.

● Each tacitly colluding firm hopes that if it does not rock the boat (via ↓P or ↑ads), then rivals will do same.

● Price leadership = 1 firm makes P decisions for group.♦ Other firms are expected to adopt P of leader without any

explicit agreement.

♦ P leader is often largest firm in industry.

● Overt collusion (where firms meet to pick P-Q) is illegal in the U.S. and rare. But tacit collusion is common.

● Each tacitly colluding firm hopes that if it does not rock the boat (via ↓P or ↑ads), then rivals will do same.

● Price leadership = 1 firm makes P decisions for group.♦ Other firms are expected to adopt P of leader without any

explicit agreement.

♦ P leader is often largest firm in industry.


Sales Maximization: Model with Interdependence IgnoredSales Maximization: Model with Interdependence Ignored

● Firms may attempt to max revenue rather than profit if:♦ control is separated from ownership

♦ compensation of managers is related to size of the firm

● Q set where MR = 0 (rather than MR = MC)♦ Recall: MR is slope of TR curve. So TR is max when MR = 0.

If MR > 0 → ↑Q to ↑TR and if MR < 0 → ↓Q to ↑TR.

● Compared to profit-max firm:♦ Higher Q

♦ Lower P

● Firms may attempt to max revenue rather than profit if:♦ control is separated from ownership

♦ compensation of managers is related to size of the firm

● Q set where MR = 0 (rather than MR = MC)♦ Recall: MR is slope of TR curve. So TR is max when MR = 0.

If MR > 0 → ↑Q to ↑TR and if MR < 0 → ↓Q to ↑TR.

● Compared to profit-max firm:♦ Higher Q

♦ Lower P

FIGURE 3. Sales-Max EquilibriumFIGURE 3. Sales-Max Equilibrium

3.75

3.69 3.75 3.80

2.5

$4.00

MR

B

D

E

AC

Pri

ce

per

Bo

x

Millions of Boxes per Year

F

MC

A

Π-max Q = 2.5m where MR =

MC. P = $4.00 and total Π = $0.20 x 2.5 m = $500,000.

Sales-max Q = 3.75m where

MR = 0. P = $3.75 and total Π = $0.06 x 3.75 m = $225,000.

Total Π (TR) is lower (higher) at point F than point E.


The Kinked Demand Curve ModelThe Kinked Demand Curve Model

● Resolve puzzle 3 –why do P in oligopolistic markets (cars or appliances) change less often than P of commodities (wheat or gold)?

● Firms think that other firms will match any P cut, but not any P increase. If true, firms face an inelastic D curve with P cuts and an elastic curve with P increases.

● Resolve puzzle 3 –why do P in oligopolistic markets (cars or appliances) change less often than P of commodities (wheat or gold)?

● Firms think that other firms will match any P cut, but not any P increase. If true, firms face an inelastic D curve with P cuts and an elastic curve with P increases.

??



● In Fig. 4, pt A is firm’s initial P = $8. ● 2 D curves pass through pt A.

♦ DD is more elastic → rivals’ P are fixed

♦ dd is less elastic → rivals match ∆P

● If firm ↓P to $7 (and rivals don’t match ↓P) → large ↑customers, so new Qd = 1,400.

● If rivals match ↓P → ↑Qd is small, so new Qd = 1,100.● If firm ↑P (and rivals don’t match ↑P) → large ↓Qd.

● In Fig. 4, pt A is firm’s initial P = $8. ● 2 D curves pass through pt A.

♦ DD is more elastic → rivals’ P are fixed

♦ dd is less elastic → rivals match ∆P

● If firm ↓P to $7 (and rivals don’t match ↓P) → large ↑customers, so new Qd = 1,400.

● If rivals match ↓P → ↑Qd is small, so new Qd = 1,100.● If firm ↑P (and rivals don’t match ↑P) → large ↓Qd.

??



● The firm’s true demand curve in Fig. 4 is DAd –a kinked demand curve.

● P tend to “stick” to their original level because ↑P → lose many customers and ↓P → gain very few customers.

● Firm will only ∆P if costs change enormously.

● The firm’s true demand curve in Fig. 4 is DAd –a kinked demand curve.

● P tend to “stick” to their original level because ↑P → lose many customers and ↓P → gain very few customers.

● Firm will only ∆P if costs change enormously.

??

FIGURE 4. The Kinked Demand Curve

FIGURE 4. The Kinked Demand Curve

0

7

Quantity per Year

Pri

ce

$8

D (Competitors’ prices are fixed)

D

1,400 1,100 1,000

(Competitors respond to price changes)

d

d

A

Typical oligopoly fears the worst. If firm cuts P then rivals will match P cut → relevant demand curve is dd. But if firm raises P then rival will not match the P increase → relevant demand curve is DD. Thus, the firm’s true demand curve is the red line “DAd.”



● MR is associated with DD and mr is associated with dd.● Overall marginal revenue curve is DBCmr.● MC = MR at pt E which shows Π-max Q for oligopolist.● Since relevant MR curve is kinked, even a moderate shift

in MC will leave Q and thereby P unchanged.● Oligopoly prices are “sticky” and do not respond to

minor cost changes.

● MR is associated with DD and mr is associated with dd.● Overall marginal revenue curve is DBCmr.● MC = MR at pt E which shows Π-max Q for oligopolist.● Since relevant MR curve is kinked, even a moderate shift

in MC will leave Q and thereby P unchanged.● Oligopoly prices are “sticky” and do not respond to

minor cost changes.

??

FIGURE 5. The Kinked Demand Curve and Sticky Prices

FIGURE 5. The Kinked Demand Curve and Sticky Prices

mr

MR

Quantity Supplied per Year

Pri

ce

$8

1,000

MC

D

D

d

d

A

E

B

C


The Game-Theory ApproachThe Game-Theory Approach

● Most widely used approach to analyze oligopoly behavior.

● Each oligopolist is seen as a competing player in a game of strategy.

● Optimal strategies are determined by examining a payoff matrix showing Π of each firm depending on P strategy that each firm follows.

● Most widely used approach to analyze oligopoly behavior.

● Each oligopolist is seen as a competing player in a game of strategy.

● Optimal strategies are determined by examining a payoff matrix showing Π of each firm depending on P strategy that each firm follows.


Games with Dominant StrategiesGames with Dominant Strategies

● Dominant strategy = one that gives the bigger payoff to the firm that selects it, no matter which of the two strategies the competitor selects.♦ E.g., Table 1., both firms have an incentive to pick low P

strategy regardless of what other firm does. If B picks high P, then A receives largest payoff choosing low P. Or if B picks low P, then A receives the largest payoff by choosing low P.

♦ “Low Price” is the dominant strategy for both firms, so both charge a low P and each earns $3m.

● Dominant strategy = one that gives the bigger payoff to the firm that selects it, no matter which of the two strategies the competitor selects.♦ E.g., Table 1., both firms have an incentive to pick low P

strategy regardless of what other firm does. If B picks high P, then A receives largest payoff choosing low P. Or if B picks low P, then A receives the largest payoff by choosing low P.

♦ “Low Price” is the dominant strategy for both firms, so both charge a low P and each earns $3m.

TABLE 1. Payoff Matrix with Dominant Strategies

TABLE 1. Payoff Matrix with Dominant Strategies

A gets $10m

B gets $10m

A gets -$2m

B gets $12m

A gets $12m

B gets -$2m

A gets $3m

B gets $3m

Firm B Strategy

High Price Low Price

Firm A Strategy

High Price

Low Price


Games with Dominant StrategiesGames with Dominant Strategies

● A market with a duopoly serves public interest better than a monopoly because of the competition created between two firms.♦ Both firms would be better off if they could charge high P. But

the presence of a competitor, forces each firm to protect itself by charging low P.

● It is damaging to the public to allow rival firms to collude on what prices to charge for their products.♦ E.g., if two firms collude in Table 1, then we end up with high

P and each earning $10m.

● A market with a duopoly serves public interest better than a monopoly because of the competition created between two firms.♦ Both firms would be better off if they could charge high P. But

the presence of a competitor, forces each firm to protect itself by charging low P.

● It is damaging to the public to allow rival firms to collude on what prices to charge for their products.♦ E.g., if two firms collude in Table 1, then we end up with high

P and each earning $10m.


Games without Dominant StrategiesGames without Dominant Strategies

● Maximin = select the strategy that yields the max payoff assuming your rival does as much damage to you as he can.

● In Table 2, A’s maximin strategy is to pick low P and earn $5m. ♦ Firm A thinks: if I chose a high P → worst outcome is B picks

a low P and I get $3m. If I chose a low P → worst outcome is B picks a low P and I get $5m.

♦ Firm A picks the strategy that offers the best of those bad outcomes.

● Maximin = select the strategy that yields the max payoff assuming your rival does as much damage to you as he can.

● In Table 2, A’s maximin strategy is to pick low P and earn $5m. ♦ Firm A thinks: if I chose a high P → worst outcome is B picks

a low P and I get $3m. If I chose a low P → worst outcome is B picks a low P and I get $5m.

♦ Firm A picks the strategy that offers the best of those bad outcomes.

TABLE 2. A Payoff Matrix without a Dominant Strategy

TABLE 2. A Payoff Matrix without a Dominant Strategy

A gets $10m A gets $3m

A gets $8m A gets $5m

High Price Low Price

High Price

Low Price

Firm B Strategy

Firm A Strategy


Repeated GamesRepeated Games

● Repeated games give players the opportunity to learn something about each other’s behavior patterns and, perhaps, to arrive at mutually beneficial arrangements.

● Table 1 shows a single round of the game. Each firm picked low P. But if games are repeated, players can escape this trap. ♦ E.g., Firm A could cultivate a reputation of “tit for tat.” Each

time B charges a high P → A would charge a high P. After a few repetitions, B learns that A always matches its P decisions. So B will see that it’s better to stick with a high P.

● Repeated games give players the opportunity to learn something about each other’s behavior patterns and, perhaps, to arrive at mutually beneficial arrangements.

● Table 1 shows a single round of the game. Each firm picked low P. But if games are repeated, players can escape this trap. ♦ E.g., Firm A could cultivate a reputation of “tit for tat.” Each

time B charges a high P → A would charge a high P. After a few repetitions, B learns that A always matches its P decisions. So B will see that it’s better to stick with a high P.


Threats and CredibilityThreats and Credibility

● Use threats to induce rivals to change their behavior.♦ E.g., retailer could threaten to double Q and ↓P to $0 if a rival

imitates its product. But this is not credible, because it hurts the retailer who is making the threat.

● A credible threat is a threat that does not harm the threatener if it is carried out.

● Old firms often use credible threats to prevent new firms from entering the industry.♦ E.g., old firm will build a larger factory than it would

otherwise want. Large factory lowers cost of ↑Q –even at low P.

● Use threats to induce rivals to change their behavior.♦ E.g., retailer could threaten to double Q and ↓P to $0 if a rival

imitates its product. But this is not credible, because it hurts the retailer who is making the threat.

● A credible threat is a threat that does not harm the threatener if it is carried out.

● Old firms often use credible threats to prevent new firms from entering the industry.♦ E.g., old firm will build a larger factory than it would

otherwise want. Large factory lowers cost of ↑Q –even at low P.

FIGURE 6. Entry and Entry-Blocking Strategy

FIGURE 6. Entry and Entry-Blocking Strategy

6 0

2 2

4 0

–2 –2

Profits (millions $) Old Firm New Firm

Possible Reactions of New Firm

Possible Choices of Old Firm

Enter

Don’t Enter

Don’t Enter

Enter

Small Factory

Big Factory


Threats and CredibilityThreats and Credibility

● In Fig. 6, best outcome for old firm is to have a small factory and no rivals.♦ But if old firm builds a small factory, it can count on new firm

entering to earn $2m. So old firm’s ↓Π to $2m.

● If old firm builds a big factory, its ↑Q will ↓P and ↓Π. Old firm now earns $4m if new firm stays out.♦ Clearly, new firm will stay out to avoid loses of $2m.

● Thus, old firm should build big factory to keep rivals out.

● In Fig. 6, best outcome for old firm is to have a small factory and no rivals.♦ But if old firm builds a small factory, it can count on new firm

entering to earn $2m. So old firm’s ↓Π to $2m.

● If old firm builds a big factory, its ↑Q will ↓P and ↓Π. Old firm now earns $4m if new firm stays out.♦ Clearly, new firm will stay out to avoid loses of $2m.

● Thus, old firm should build big factory to keep rivals out.


Monopolistic Competition, Oligopoly, & Public WelfareMonopolistic Competition, Oligopoly, & Public Welfare

● Oligopolistic behavior is so varied that it is hard to come to a simple conclusion about welfare implications.

● In many circumstances, the behavior of monopolistic competitors and oligopolists falls short of the social optimum.

● Excess capacity theorem suggests monopolistic competition can lead to inefficiently high production costs.

● Oligopolists may organize into successful cartels to ↓Q and ↑P.

● Oligopolistic behavior is so varied that it is hard to come to a simple conclusion about welfare implications.

● In many circumstances, the behavior of monopolistic competitors and oligopolists falls short of the social optimum.

● Excess capacity theorem suggests monopolistic competition can lead to inefficiently high production costs.

● Oligopolists may organize into successful cartels to ↓Q and ↑P.


Monopolistic Competition, Oligopoly, & Public WelfareMonopolistic Competition, Oligopoly, & Public Welfare

● When an oligopolistic market is perfectly contestable –if firms can enter and exit without losing $ they invested –then (P,Q) of firms is likely to be socially efficient.

♦ E.g., airplanes, trucks, and barges can easily be moved.

● Constant threat of entry forces oligopolists to keep their prices down and their costs low.

● When an oligopolistic market is perfectly contestable –if firms can enter and exit without losing $ they invested –then (P,Q) of firms is likely to be socially efficient.

♦ E.g., airplanes, trucks, and barges can easily be moved.

● Constant threat of entry forces oligopolists to keep their prices down and their costs low.


Comparing the Four Market FormsComparing the Four Market Forms

● Perfect competition and pure monopoly are rare.● Most firms are monopolistically competitive, but

oligopoly firms account for largest share of economy’s output.

● Π = 0 in LR under perfect competition and monopolistic competition because of free entry and exit.♦ Thus, P = AC in LR under these 2 market forms.

● Π-max firm under any market form selects Q by setting MR = MC. ♦ However, oligopolists may not set MC = MR when choosing Q

–e.g., if firm max sales.

● Perfect competition and pure monopoly are rare.● Most firms are monopolistically competitive, but

oligopoly firms account for largest share of economy’s output.

● Π = 0 in LR under perfect competition and monopolistic competition because of free entry and exit.♦ Thus, P = AC in LR under these 2 market forms.

● Π-max firm under any market form selects Q by setting MR = MC. ♦ However, oligopolists may not set MC = MR when choosing Q

–e.g., if firm max sales.


Comparing the Four Market FormsComparing the Four Market Forms

● Perfectly competitive firm and industry efficient allocation of resources.

● Monopoly inefficient allocation of resources by ↓Q and ↑P.

● Monopolistic competition inefficient allocation of resources through excess capacity.

● Under oligopoly, almost anything can happen, impossible to generalize about its vices or virtues.

● Perfectly competitive firm and industry efficient allocation of resources.

● Monopoly inefficient allocation of resources by ↓Q and ↑P.

● Monopolistic competition inefficient allocation of resources through excess capacity.

● Under oligopoly, almost anything can happen, impossible to generalize about its vices or virtues.

TABLE 3. Attributes of the Four Market Forms

TABLE 3. Attributes of the Four Market Forms

between competition and monopoly

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