industry supply

Industry Supply

Supply From A Competitive Industry

How are the supply decisions of the many individual firms in a competitive industry to be combined to discover the market supply curve for the entire industry?

The aggregation of the behavior of each individual producer will enable us to understand how the market as a whole functions.


Since every firm in the industry is a price-taker, total quantity supplied at a given price is the sum of quantities supplied at that price by the individual firms.

Short-Run Supply

In a short-run the number of firms in the industry is temporarily fixed.

Let n be the number of firms;i = 1, … ,n.

Si(p) is firm i’s supply function.

Short-Run Supply

In a short-run the number of firms in the industry is temporarily fixed.

Let n be the number of firms;i = 1, … ,n.

Si(p) is firm i’s supply function. The industry’s short-run supply

function isS p S pi

i

n( ) ( ).

1


p

S1(p)

p

S2(p)

Firm 1’s Supply Firm 2’s Supply


p

S1(p)

p

S2(p)p

p’

p’

S1(p’)

S1(p’)


S(p) = S1(p) + S2(p)

Industry’s Supply


p

S1(p)

p

S2(p)p

S(p) = S1(p) + S2(p)

p”

p”

S1(p”)

S1(p”)+S2(p”)

S2(p”)


Industry’s Supply


p

S1(p)

p

S2(p)p


S(p) = S1(p) + S2(p)

Industry’s Supply

Short-Run Industry Equilibrium

In a short-run, neither entry nor exit can occur.

Consequently, in a short-run equilibrium, some firms may earn positive economic profits, others may suffer economic losses, and still others may earn zero economic profit.


Market demand

Short-run industrysupply

pse

Yse Y

Short-run equilibrium price clears themarket and is taken as given by each firm.


y1 y2 y3

ACs

ACs ACs

MCs

MCs

MCs

y1* y2

* y3*

pse

Firm 1 Firm 2 Firm 3


y1 y2 y3

ACs

ACs ACs

MCs

MCs

MCs

y1* y2

* y3*

pse


> 0 < 0 = 0


y1 y2 y3

ACs

ACs ACs

MCs

MCs

MCs

y1* y2

* y3*

pse


Firm 1 wishesto remain inthe industry.

Firm 2 wishesto exit fromthe industry.

Firm 3 isindifferent.

> 0 < 0 = 0

Long-Run Industry Supply

In the long-run every firm now in the industry is free to exit and firms now outside the industry are free to enter.

The industry’s long-run supply function must account for entry and exit as well as for the supply choices of firms that choose to be in the industry.

How is this done?


Positive economic profit induces entry. Economic profit is positive when the

market price pse is higher than a firm’s

minimum av. total cost; ps

e > min AC(y). Entry increases industry supply,

causing pse to fall.

When does entry cease?


S2(p)

Mkt. DemandAC(y)MC(y)

y

A “Typical” FirmThe Marketp p

YSuppose the industry initially containsonly two firms.

Mkt.Supply


S2(p)


y


Y

p2 p2

Then the market-clearing price is p2.


S2(p)


y


Y

p2 p2

y2*

Then the market-clearing price is p2.Each firm produces y2* units of output.


S2(p)


y


Y

p2 p2

y2*

> 0

Each firm makes a positive economicprofit, inducing entry by another firm.


S2(p)

S3(p)


y


Y

p2 p2

Market supply shifts outwards.y2*


S2(p)

S3(p)


y


Y

p2 p2

Market supply shifts outwards.Market price falls.

y2*


S2(p)

S3(p)


y


Y

p3

Each firm produces less.y3*

p3


S2(p)

S3(p)


y


Y

p3

Each firm produces less.Each firm’s economic profit is reduced.

y3*

p3 > 0


S3(p)


y


Y

p3

Each firm’s economic profit is positive.Will another firm enter?

y3*

p3 > 0


S4(p)S3(p)


y


Y

p3

Market supply would shift outwards again.y3*

p3


S4(p)S3(p)


y


Y

p3

Market supply would shift outwards again.Market price would fall again.

y3*

p3


S4(p)S3(p)


y


Y

p4

Each firm would produce less again.y4*

p4


S4(p)S3(p)


y


Y

p4

Each firm would produce less again. Eachfirm’s economic profit would be negative.

y4*

< 0p4


S4(p)S3(p)


y


Y

p4

Each firm would produce less again. Eachfirm’s economic profit would be negative.So the fourth firm would not enter.

y4*

< 0p4


The long-run number of firms in the industry is the largest number for which the market price is at least as large as min AC(y).


Suppose that market demand is large enough to sustain only two firms in the industry.

If market demand increases, the market price rises, each firm produces more, and earns a higher economic profit.


S2(p)

S3(p)


y


Y

p2”

y2*

p2”


S2(p)

S3(p)


y


Y y2*

p2” p2”


S2(p)

S3(p)


y


Y y2*

Notice that a 3rd firm will not enter since itwould earn negative economic profits.

p2” p2”


As market demand increases further, the market price rises further, the two incumbent firms each produce more and earn still higher economic profits -- until a 3rd firm becomes indifferent between entering and staying out.


S2(p)

S3(p)


y


Y y2*

p2” p2”


S2(p)

S3(p)


y


Y y2*

p2’” p2’”


S2(p)

S3(p)


y


Y y2*

A third firm can now enter, causing all firmsto earn zero economic profits.

p2’” p2’”


S2(p)

S3(p)


y


Y y2*

The only relevant part of the short-runsupply curve for n = 2 firms in the industry.

p2’” p2’”


How much further can market demand increase before a fourth firm enters the industry?



y


Y

p3’

y3*

A 4th firm would now earn negativeeconomic profits if it entered the industry.

p3’

S3(p)S4(p)


S3(p)

Mkt. Demand

AC(y)MC(y)

y


Y y3*

S4(p)

But now a 4th firm would earn zeroeconomic profit if it entered the industry.

p3’ p3’


S3(p)

Mkt. Demand

AC(y)MC(y)

y


Y y3*

S4(p)p3’ p3’

The only relevant part of the short-runsupply curve for n = 3 firms in the industry.


Continuing in this manner builds the industry’s long-run supply curve, one section at-a-time from successive short-run industry supply curves.


AC(y)MC(y)

y

A “Typical” FirmThe MarketLong-RunSupply Curve

p p

Y y3*

Notice that the bottom of each segment ofthe supply curve is min AC(y).


As each firm gets “smaller” relative to the industry, the long-run industry supply curve approaches a horizontal line at the height of min AC(y).


AC(y)

MC(y)

y


p p

Y y*

The bottom of each segment of the supplycurve is min AC(y). As firms get “smaller”the segments get shorter.


AC(y)

MC(y)

y


p p

Y y*

In the limit, as firms become infinitesimallysmall, the industry’s long-run supplycurve is horizontal at min AC(y).

Long-Run Market Equilibrium Price In the long-run market equilibrium,

the market price is determined solely by the long-run minimum average production cost.

This means that profits will be close to zero for industries with free entry. Long-run market price is

p AC ye

y

min ( ).0

Zero Profits

In an industry with free entry, profits will be driven down to zero, because as long as profits are positive there is an incentive for new firms to enter the market.

Zero Profits When profits (in the economic sense of

the word) are zero, the industry stops growing, but does not die. This is because all factors of production are being remunerated at their opportunity cost, i.e. at the rate they would earn elsewhere in the economy.

The existence of positive profits in an industry constitutes a signal that outputs are being more valued than inputs and so it makes sense that more firms enter the industry in order to supply a greater amount of output.

Long-Run Market Equilibrium Price

In most competitive industries, there are no restrictions against new firms entering the market, i.e. the industry exhibits free entry. But in some cases, industries exhibit barriers to entry, that may have to do with legal restrictions imposed by the government or with the existence of a limited supply of a certain input.

Fixed Inputs and Economic Rent Since not all industries have free entry,

some of them will have a fixed number of firms. There are two main reasons that preclude free entry in an industry:a) There are some inputs that are fixed by nature for the whole economy, even in the long run. This is typically the case of extractive industries, such as oil, precious metals, and also of agriculture as the extension of arable land is limited.

Fixed Inputs and Economic Rent

b) There are inputs that are fixed by law. In fact, there are industries for which the government imposes restrictions, in the form of licenses and permits. Examples of these industries include the taxi industry or the drugstore/pharmacy industry (in Portugal, at least). Licensing is a barrier to entry into a competitive industry.


The absence of free entry could lead us to think that in these cases profits would not be driven down to zero. . . but provided that we keep valuing each and every input at its opportunity cost, profits will turn out to be zero as well.


An input (e.g. an operating license) that is fixed in the long-run causes a long-run fixed cost, F.

Long-run total cost, c(y) = F + cv(y). And long-run average total cost,

AC(y) = AFC(y) + AVC(y). In the long-run equilibrium, what will

be the value of F?


Think of a firm that needs an operating license -- the license is a fixed input that is rented but not owned by the firm.

If the firm makes a positive economic profit then another firm can offer the license owner a higher price for it. In this way, all firms’ economic profits are competed away, to zero.


So in the long-run equilibrium, each firm makes a zero economic profit and each firm’s fixed cost is its payment for its operating license.


Economic rent is the payment for an input that is in excess of the minimum payment required to have that input supplied.

Each license essentially costs zero to supply, so the long-run economic rent paid to the license owner is the firm’s long-run fixed cost.


Think of a typical Portuguese drugstore. To run one, a firm must acquire a permit (alvará) from the government. If we value all inputs except the alvará we end up with Z euros per year of “profits”. However, in a competitive market, the value of the alvará per year is precisely Z euros.


Therefore, if the firm could rent the alvará for Z euros, it would be indifferent between running the drugstore or renting the alvará and go out of the drugstore business. So the rent is the opportunity cost of the alvará, which means that if we take this cost into account, we will reach the conclusion that profits are also zero in this case.


In fact, whenever there is a fixed input that is preventing free entry into an industry, there will be an equilibrium rental rate for that input. This rental rate guarantees that the profits (in the economic sense) of a new entrant will be zero.


If the fixed input is not to be rented but to be sold outright, then the price of the input must, in equilibrium, be equal to the present value of the future stream of rental payments. In Portugal, alvarás are sold rather than rented, so its price is supposed to give the present value of future rents.

industry supply

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