week 7 presentation is from: class notes of prof. gerald shively purdue university (agec 640:...

Week 7

Presentation is from:

Class notes of Prof. Gerald Shively

Purdue University

(AGEC 640: Agricultural Development and Policy)

Market Equilibrium and Social Welfare

Market equilibrium with trade & policyThe story so far…

Up to now we’ve taken prices as given, asking how households respond with substitution in production:

Qty. of corn(bu/acre)

Qty. of labor (hours/acre)

Qty. of corn(bu/acre)

Qty. of beans(bushels/acre)

Pl/Pc Pl/Pc’ Pb/PcPb/Pc’

more corn, more input use

more corn, less other outputs

Each price change affects the

household’s production choices,

input use and income

…and on the consumption side:

Qty. ofcorn

Qty. of all other goods

The household’s total income and expenditure at Po/Pc

The household’s total income and expenditure at Po/Pc’

Each price change affects the household’s

production choices, input use and income

Households respond to price changes with both income and substitution effects:

income effect

substitution effect

Adding up production decisions across households gives us an aggregate supply curve:

Price($/lb)

Quantity Produced (thousands of tons/yr)

each producer’s production is added horizontally

each price is every participating household’s

marginal cost of production, in terms of other goods

…but remember at each price some households are not trading!

…and adding up households’ consumption decisions gives us an aggregate demand curve:

Price($/lb)

Quantity Consumed(thousands of tons/yr)

each consumer’s demand is added horizontally

each price is every participating household’s willingness

and ability to pay

…but again at each price some households are not trading!

…so the aggregate of all households’ production costs and willingness-to-pay is:

P($/lb)

Q(tons)

MC

WTP

So, what price are we likely to observe in the market?

…almost all interesting cases have something else we’d need to draw!

What price would we observe if these people can trade with the rest of the world?

P($/lb)

Q(tons)

MC

WTP

We need to draw a similar diagram for them, and for the trade between us and them

P($/ton)

“Us” (e.g. Turkey.)

P($/ton)

The Rest of the World (RoW)

Q(tons)

Trade between us & them

Starting with foreign supply and demand:

P($/ton)

Turkey

P($/ton)

The Rest of the World

Q(tons)

Trade between Turkey and the

world

Note we’ve drawn the same price axis for Turkey and RoW (ignoring exchange rates)

Then we can draw Turkey’swillingness to trade with the RoW:

P($/ton)

Turkey

P($/ton)


Q(tons)

Trade between Turkey and RoW

Q(tons)

The Turkey’s “excess demand curve” in trade, i.e. the amount demanded at any price that cannot be met by domestic supply.

ED

and RoW’s willingness to trade…

P($/ton)

Turkey

P($/ton)


Q(tons)

Trade between Turkey and

ROW

Q(tons)

ES

Q(thou. tons)

ED

The “excess supply curve” in trade shows the amount supplied by the world at any price that exceeds the world price.

World Price Clearing…

P($/lb)

Turkey

P($/lb)


Q(tons)

Trade between Turkey and

ROW

Q(tons)

Because total quantity in the RoW is large, the “excess supply” curve is almost flat when graphed on the same axis as Turkey’s curves.

International markets clear when ED=ED

ES

Q(1000 tons)

ED

The large size of the rest of the world allows us to simplify the diagram

P($/ton)

Turkey

P($/ton)


Q(tons)

Trade between us and them

Q(tons)

ES

Q(thou. tons)

ED

the simplifying assumption that this line is horizontal is called the “small country” assumption.

The small-country assumption allows a single diagram to both Turkey & the RoW

P($/ton)

Turkey

P($/lb)


Q(tons)

Trade between Turkey

Q(tons)

ES

Q(thou. tons)

ED

As the “world” price would not be affected by changes in Turkey.

Pw

For many important traded products, prices are determined by the world’s supply-demand balance,

not local production and consumption.

P($/ton)

Turkey

Q(tons)

Pw

Local supply and demand determine production, consumption and trade, at a price given by the big (bad?) world market

But then there’s policy!

Policies that help producersraise Pd above Pt

export taxes or quotas

Policies on exports

import tariffsorquotas

importsubsidies(rarely seen)

Policies on imports

exportsubsidies

Policies that help consumers lower Pd below Pt

Policies that work through trade affect both producers and consumers.

S (producers’ marginal cost)tax

S’ (market supply, after taxes)Policies that tax production affect a market like this:

and policies that tax consumption look like this:

D’ (market demand, after taxes)

D (consumers’ demand)

Taxes restrict the market supply or demand, shifting them to the left…

But what about “domestic” policies?

tax

Policies that subsidize production work like this:

and policies that subsidize consumption work like this:

S (producers’ marginal cost)subsidy

S’ (market supply, after taxes)

D’ (market demand, after subsidies)subsidy

D (consumers’ demand)

Subsidies expand market supply or demand -- shift curves to the right.

Combining these concepts, we have six possiblepolicies in markets for importables

taxesorrestrictions

subsidiesorencouragements

on trade on production on consumption

affect bothprod. & cons.

affect onlyproduction

affect onlyconsumption

…and six possible policies in markets for exportables:

taxesorrestrictions

subsidiesorencouragements

on trade on production on consumption

affect bothprod. & cons.

affect onlyproduction

affect onlyconsumption

Can we say anything about “social welfare”?

• What can we infer from the diagrams about how price changes affect consumer or producer welfare?

• What can we infer about net effects on “social” welfare?

• The simplest and most widely used approach is to compute changes in aggregate “economic surplus”:– areas on a supply-demand diagram

– measured in terms of money (=price X quantity)

– but equally relevant in a non-monetized setting…

• To see strengths and limitations of econ surplus approach we should start with fundamentals

Qobs.

Pobs.

as qty. rises, the gap between the curves falls…

Criteria:How could we evaluate a change?

until this marginal economic surplus reaches zero at the equilibrium

Qobs.

Pobs.

The Hines articleexplains how this area came to be the workhorse definition of “social welfare” in applied policy work, despiteits limitations relative to otherdefinitions of social welfare.

“Economic surplus” is simply the area between S & D curves

Qobs.

Pobs.

For example, if new technology reduces marginal cost by 10%,

There is a very close link between “positive” economics (for prediction)

and “normative” economics (for evaluation)

Q’

P’ we can predict that the new P’ will be lower and the new Q’ will be higher.

A lower price means producers may lose…

but the logic of economic surplus means there must be a net gain to society as a whole.

Equilibrium = Optimum ?!

Qobs.

Pobs.

If the equilibrium is the social optimum, do we live in the best of all possible worlds?

If you have no other information,you cannot say something else would be better!

Econ 101 vs. Econ 102

Qobs.

Pobs.

To continue the analysis, weneed to know something about some other costs and benefits incurred in this market.

• The question for welfare economics is, what can one infer about “aggregate welfare” from individual choices, which are assumed to be optimizing an unknown utility function.

• The answer is…not much…unless we make additional, quite strong assumptions

e.g. all consumers are similar in certain ways,or face prices that are similar in certain

ways“Welfare economics” is about those assumptions and their effects. Most are not testable…

… we should remember…

• The Pareto Principle– A “Pareto improvement” is preferred by at least one person, and

dispreferred by no one.

– Very many situations are already “Pareto optimal”, and designing Pareto-improving policies is very difficult!

• The “first theorem” of welfare economics– A perfectly competitive equilibrium would be Pareto optimal

(because everyone faces identical prices)

• The “second theorem” of welfare economics– Any P. optimum can be reached by a p.c.e. with transfers

(but only if everyone can use the transfers to adjust consumption!)

…and, more practically, the Compensation Principle

• Is “Pareto improvement” needed for a change to be good?– what if many gain, and only one person loses?– what if the gains are much larger than the losses?– would the gains have to be redistributed immediately for the

change to be socially desirable?• Usually, we invoke the “compensation principle”:

– we use the term “Pareto improvement” loosely, to mean a potentially Pareto-improving change, whose gainers could (but don’t necessarily) compensate losers and still be better off.

– Income and wealth is constantly being (re)distributed through various mechanisms; this way we separate the questions, and do not expect changes to generate gains and also redistribute them!

• In real life, “reform packages” often involve some compensation, to those who could block the change.

Arnold Harberger and the Triumph of Economic Surplus

• Harberger’s three postulates (untestable!):– marginal willingness to pay is value in consumption– marginal supply price is cost of production– economists should be impartial, and count everyone’s

money equally.

• Surprisingly, this turns out to lead towards political positions that are often quite “liberal”, – because actual politics often involves “King John

redistribution” (from poorer to richer people) and “vested interests” (that block pro-poor changes).

• A major determinant of economic growth is the extent to which governments follow Harberger…

Qty. of “a” goods

Economic surplus treats the market as a household

Qty of “b”Qb Qb

Qa

Price of “b” goods

Pb

slope of income line =-Pb/Pa

highest indifference level in a household model

Qb

QaMRS

curve indiff. of slope

highest economic surplus in a market model

equilibrium among

optimizing people in a

perfectly competitive

market

We can divide “economic surplus” into:

Qb


Pb

“Consumer surplus” :area between price paid

and the demand curve

“Producer surplus” :area between price received

and the supply curve

The sum of everyone’s gains/lossesis society’s total economic surplus

Qty. of “a” goods

Trade creates a distinction between production and consumption – e.g. when we start selling:

Qty of “b”


Qty of “b”

A B

AProducer surplus in “b” declines by:

B

…but consumer surplus in “b” rises by: BA

==> net social gain from trade in “b” is:Net gain from trade

Decline in production of “b”

Increase in consumption of “b”


New technologies also have very different impacts on producers and consumers

A B

C

Net Econ. Surplus Gain = B+C

Consumer Surplus Gain = A+BProducer Surplus Change = C-A

If demand is very inelastic, and supply is very elastic, then innovation causes producer surplus to fall.

This is “Cochran’s Treadmill”, pushing ag. producers to become ag. consumers.Qty of “b”

…but note that if a good is traded at a fixed price…



With no trade With free trade

innovation does not affect consumers;all gains go to producers!

Qty of “b” Qty of “b”

No innovation

With innovation

No innovation

With innovation

So what do we see, and why do we see it?The incidence of each policy is price change X qty. affected, or economic surplus – a useful measure of welfare change

P($/lb)

Qp QcM

For example, the U.S. market for avocadoes

Pw

Pus

QpQc

A B C D

Consumers lose ABCD

Producers gain AWho gains C?

In this case, avocado growers’ associations were given import quotas, and so captured the “quota rent” C from buying at Pw and selling at Pus, as well as the increased producer surplus A.

Policy is an import quota (M)

Areas B and D are Harberger triangles, permanent losses to domestic economy.

P($/lb)

Turkey

PwPus A B C D

Production efficiency losses, where MC is above Pw

Consumption efficiency losses, where WTP is above Pw

Comparing instruments across markets

Qp’ Qc’

PwPus

Qp Qc

A B C D

An import quota instrument (M’)

C.S. change: -ABCDP.S. change: +Aquota rent: +C net change: -B D

PwPus A B C D

An import tariff instrument (t)

Pw+t

Qp’ Qc’Qp Qc

Note that this “tariff-quota equivalence” is limited; if there are changes in S, D or Pw, the two policies lead to different responses!

S+quotaS

C.S. change: -ABCDP.S. change: +Atariff revenue: +C net change: -B D

What about policy on exports: If trade is good, surely more trade is better?

QsQd

CS loss: area ABPS gain: area ABCDESubsidy cost: area BCDEFNet loss: area BF

A D E

Ptrade

Pdom CB F

Qd’ Qs’

Remember it’s not trade as such, but free trade that’s desirable (at least in this model)

an export subsidy:

Some conclusions on market equilibrium and social welfare

• Different market structures will lead to different equilibrium outcomes – To the extent that buyers or sellers don’t trust each other, quantity sold would go

to zero -- unless remedied by trust in a brand or third-party certification– To the extent that buyers or sellers are protected from competition by barriers to

entry, they won’t act competitively -- won’t be “price takers”

• Different definitions of “welfare” lead to different policy preferences

• For policy analysis in this class we assume:– that equilibria are perfectly competitive– that “social welfare” is proportional to economic surplus

These are the simple but powerful techniques, that give us many non-obvious and yet useful results.

week 7 presentation is from: class notes of prof. gerald shively purdue university (agec 640:...

Documents

income slide

ed slide

world qtons trade

policy slide

ton turkey p

draw slide

world row qtons trade

world price clearing