Week 7 Presentation is from: Class notes of Prof. Gerald Shively Purdue University (AGEC 640:...
-
Upload
matilda-king -
Category
Documents
-
view
213 -
download
0
Transcript of 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)
Slide 2
Market Equilibrium and Social Welfare
Slide 3
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
Slide 4
…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
Slide 5
Adding up production decisions across households gives us an aggregate supply curve:
Price($/lb)
Quantity Produced (thousands of tons/yr)
each producer’s production is added horizontally
each price is every participating household’s
marginal cost of production, in terms of other goods
…but remember at each price some households are not trading!
Slide 6
…and adding up households’ consumption decisions gives us an aggregate demand curve:
Price($/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!
Slide 7
…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)
The Rest of the World
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)
The Rest of the World
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)
The Rest of the World
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
Slide 14
The large size of the rest of the world allows us to simplify the diagram
P($/ton)
Turkey
P($/ton)
The Rest of the World
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.
Slide 15
The small-country assumption allows a single diagram to both Turkey & the RoW
P($/ton)
Turkey
P($/lb)
The Rest of the World
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
Slide 16
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
Slide 17
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.
Slide 18
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
Slide 19
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.
Slide 20
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
Slide 21
…and six possible policies in markets for exportables:
taxesorrestrictions
subsidiesorencouragements
on trade on production on consumption
affect bothprod. & cons.
affect onlyproduction
affect onlyconsumption
Slide 22
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.
Slide 28
• 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…
Slide 29
… 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!)
Slide 30
…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.
Slide 31
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…
Slide 32
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
Slide 33
We can divide “economic surplus” into:
Qb
Price of “b” goods
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
Slide 34
Qty. of “a” goods
Trade creates a distinction between production and consumption – e.g. when we start selling:
Qty of “b”
Price of “b” goods
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”
Slide 35
Price of “b” goods
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”
Slide 36
…but note that if a good is traded at a fixed price…
Price of “b” goods
Price of “b” goods
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
Slide 37
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)
Slide 38
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
Slide 39
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
Slide 40
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:
Slide 41
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.