Post on 21-Jul-2020
Admin RFH Curves E & Policy Elasticities Paper Recap
Lecture 3:Elasticity
September 12, 2017
Admin RFH Curves E & Policy Elasticities Paper Recap
Overview
Course Administration
Ripped from the Headlines
Demand Curves Are Not Linear
Elasticity and Policy
Many Types of Elasticity
Paper Assignment
Recap
Admin RFH Curves E & Policy Elasticities Paper Recap
Course Administration
1. Return problem sets
2. Problem Set 3 posted
3. RFH updated – I emailed all relevant parties, but pleasedouble-check
4. Any questions or outstanding issues?
Admin RFH Curves E & Policy Elasticities Paper Recap
Problem Set 1: Moving Along the Demand Curve
• “I bought more blazers than I was planning to because theprice was lowered.”
• bought turkey when it was on sale – wouldn’t have bought itotherwise
Admin RFH Curves E & Policy Elasticities Paper Recap
Problem Set 1: Shifts of the Demand Curve
• “When I moved to DC and started spending much more timein the hot sun” demand for sunscreen shifted outward
• new job → more income → more restaurant eating, or anoutward shift of the demand for restaurant eating
Admin RFH Curves E & Policy Elasticities Paper Recap
How What You’re Learning is Policy-RelevantRipped from Headlines presentation(s)
As a reminder, next week
Afternoon
Finder Presenter
Ilham Dehry Rajan BansalCaroline Davis Jake RettigAhoefa Ananouk Jessica Blackband
Evening
Finder Presenter
Kathleen Gayle Vanessa LopezKrystin Roehl Marissa EsthimerErika Ross Deon Glaser
Admin RFH Curves E & Policy Elasticities Paper Recap
Demand Curves Not Linear
Admin RFH Curves E & Policy Elasticities Paper Recap
Demand Curves are Not Linear
1. What do we mean by linear?
2. Implications of linear curve
3. Building a non-linear curve
4. Example of why the shape matters
Admin RFH Curves E & Policy Elasticities Paper Recap
What Do We Mean By Linear?
• A linear function can be written as y = mx + b
• If b is zero (y = mx), then a 5-unit change in x → change iny equal to 5*m-unit change in x
• If b is not zero, this isn’t exactly true. However, the slope isalways the same everywhere
Admin RFH Curves E & Policy Elasticities Paper Recap
Implications of a Linear Demand Curve
• There is a price sufficiently high that no one wants toconsume the good
• At a price of zero, there is a finite quantity demanded
• Implies that many small changes in price always have thesame impact as an equivalent large change in price
→ thismay be quite wrong
Admin RFH Curves E & Policy Elasticities Paper Recap
Implications of a Linear Demand Curve
• There is a price sufficiently high that no one wants toconsume the good
• At a price of zero, there is a finite quantity demanded
• Implies that many small changes in price always have thesame impact as an equivalent large change in price → thismay be quite wrong
Admin RFH Curves E & Policy Elasticities Paper Recap
Where a Demand Curve Comes FromThanks to Hal Varian’s textbook
Let’s assume we’re interested in the market for apartments in amedium-sized college town. Further assume that
• there are two types of apartments: near and far from university
• near apartments are better
• if you don’t get an apartment near, you can get one far at aknown fixed price
• all apartments are identical
• each person wants only one apartment
We are interested in the price of the near apartments.
Admin RFH Curves E & Policy Elasticities Paper Recap
Putting Together a Demand Curve
• Reservation price is the “maximum willingness to pay forsomething”
• What is the highest reservation price of anyone in thismarket? → this is the top of the demand curve
• As we lower the price one dollar, how many additional peoplewant an apartment? This is Q
• Another dollar? This is the next (Q,P) on the curve
Admin RFH Curves E & Policy Elasticities Paper Recap
Putting Together a Demand Curve: In Pictures
P
Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Putting Together a Demand Curve: In Pictures
P
Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Putting Together a Demand Curve: In Pictures
P
Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Putting Together a Demand Curve: In Pictures
P
Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Putting Together a Demand Curve: In Pictures
P
Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Putting Together a Demand Curve: In Pictures
P
Q
Admin RFH Curves E & Policy Elasticities Paper Recap
With Many Steps, Imagine a Curve
P
Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Why the Shape of the Curve Matters: Avocados!
• 1914 US puts limits on imports of Mexican avocados
• 1994 North American Free Trade Agreement (NAFTA) passes
• 2004 USDA agrees to year-round avocado imports fromMexico
• Domestic producers of avocados• form expectations from part of demand curve they observe• except that increase in Q will lead to decline in P
• What happens?
Almost no change in P, big increase in Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Why the Shape of the Curve Matters: Avocados!
• 1914 US puts limits on imports of Mexican avocados
• 1994 North American Free Trade Agreement (NAFTA) passes
• 2004 USDA agrees to year-round avocado imports fromMexico
• Domestic producers of avocados• form expectations from part of demand curve they observe• except that increase in Q will lead to decline in P
• What happens? Almost no change in P, big increase in Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Three (Not Mutually Exclusive) ExplanationsOr, Is Everything We’ve Learned Wrong?
1. Demand curve is not linear
2. “Price” for big customers includes reliability of supply, so true“price” fell → Q ↑
3. Demand increases
Admin RFH Curves E & Policy Elasticities Paper Recap
E.1.: Demand Curve is Not LinearThe World Before NAFTA
P
Q
SUSA, weather good
D
Admin RFH Curves E & Policy Elasticities Paper Recap
E.1.: Demand Curve is Not LinearWhere Is World Supply?
P
Q
SUSA, weather good
SUSA, weather bad
D
Admin RFH Curves E & Policy Elasticities Paper Recap
E.1.: Demand Curve is Not LinearIf You Think Demand is Linear, What Happens?
P
Q
SUSA, weather good
SUSA, weather bad
D
SWorld
Admin RFH Curves E & Policy Elasticities Paper Recap
E.1.: Demand Curve is Not LinearWhy Is This Unlikely to Have Been the Case?
P
Q
SUSA, weather good
SUSA, weather bad
D
SWorld
Admin RFH Curves E & Policy Elasticities Paper Recap
E.1.: Demand Curve is Not LinearCurved Demand Is One Explanation
P
Q
SUSA, weather good
SUSA, weather bad
D
SWorld
Admin RFH Curves E & Policy Elasticities Paper Recap
E.2.: “Price” for big customers falls
• Elsewhere, I learned that after the introduction of Mexicanavocados, big chains considered putting them in menus
• Major cost component for big chain input is reliability• Mexican supply guarantees year-round supply• And more reliable supply
• Thus, for big firms, outward supply shift understates truedecrease in price, and can explain large change in Q
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity and Policy
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity
• Elasticity measures the change in quantity for a given changein price
• Absolutely crucial for policy decisions
• Formally, percentage change in one value relative topercentage change in another
• In math, elasticity is
E =%∆Q
%∆P
Admin RFH Curves E & Policy Elasticities Paper Recap
Drawing Perfectly Inelastic and Perfectly Elastic Demandand Supply
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity and Policy
• “Among the models that CBO uses to analyze the economiceffects of changes in federal fiscal policy is a life-cycle growthmodel. That model requires an estimate of [the elasticity oflabor supply with respect to price]. .... CBO incorporates intoits analyses an estimate of the [this] elasticity that rangesfrom 0.27 to 0.53, with a central estimate of 0.40.”
• → a 1% change in wages causes a 0.4% change in labor supply
• Arlington and Uber• From the article, what policy is Arlington considering?• How do you think this policy changes the total price of using
transit?• Do you think it’s a good idea to linearly extrapolate from the
original demand curve?
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity and Policy
• “Among the models that CBO uses to analyze the economiceffects of changes in federal fiscal policy is a life-cycle growthmodel. That model requires an estimate of [the elasticity oflabor supply with respect to price]. .... CBO incorporates intoits analyses an estimate of the [this] elasticity that rangesfrom 0.27 to 0.53, with a central estimate of 0.40.”
• → a 1% change in wages causes a 0.4% change in labor supply
• Arlington and Uber• From the article, what policy is Arlington considering?
• How do you think this policy changes the total price of usingtransit?
• Do you think it’s a good idea to linearly extrapolate from theoriginal demand curve?
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity and Policy
• “Among the models that CBO uses to analyze the economiceffects of changes in federal fiscal policy is a life-cycle growthmodel. That model requires an estimate of [the elasticity oflabor supply with respect to price]. .... CBO incorporates intoits analyses an estimate of the [this] elasticity that rangesfrom 0.27 to 0.53, with a central estimate of 0.40.”
• → a 1% change in wages causes a 0.4% change in labor supply
• Arlington and Uber• From the article, what policy is Arlington considering?• How do you think this policy changes the total price of using
transit?
• Do you think it’s a good idea to linearly extrapolate from theoriginal demand curve?
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity and Policy
• “Among the models that CBO uses to analyze the economiceffects of changes in federal fiscal policy is a life-cycle growthmodel. That model requires an estimate of [the elasticity oflabor supply with respect to price]. .... CBO incorporates intoits analyses an estimate of the [this] elasticity that rangesfrom 0.27 to 0.53, with a central estimate of 0.40.”
• → a 1% change in wages causes a 0.4% change in labor supply
• Arlington and Uber• From the article, what policy is Arlington considering?• How do you think this policy changes the total price of using
transit?• Do you think it’s a good idea to linearly extrapolate from the
original demand curve?
Admin RFH Curves E & Policy Elasticities Paper Recap
Many Types of Elasticity
Admin RFH Curves E & Policy Elasticities Paper Recap
Many Types of Elasticities
• Price elasticity of demand and supply
• Elasticity terms
• Income elasticity of demand
• Cross-price elasticity of demand
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity of Supply and Demand Reminder
• In general, we expect ED
< 0
• And ES > 0
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity of Supply and Demand Reminder
• In general, we expect ED < 0
• And ES
> 0
Admin RFH Curves E & Policy Elasticities Paper Recap
Elasticity of Supply and Demand Reminder
• In general, we expect ED < 0
• And ES > 0
Admin RFH Curves E & Policy Elasticities Paper Recap
Useful Elasticity Terms
• Unit elastic, |E | = 1: any percent changes in prices areequally matched by percent changes in Q
• Elastic, ∞ > |E | > 1: responsiveness of numerator greaterthan change in denominator
• Inelastic, 0 < |E | < 1: responsiveness of numerator less thanchange in denominator
• Perfectly inelastic, |E | = 0: no change in numerator forchange in denominator
• Perfectly elastic, |E | =∞: infinite change in numerator forchange in denominator
Admin RFH Curves E & Policy Elasticities Paper Recap
Useful Elasticity Terms
• Unit elastic, |E | = 1: any percent changes in prices areequally matched by percent changes in Q
• Elastic, ∞ > |E | > 1: responsiveness of numerator greaterthan change in denominator
• Inelastic, 0 < |E | < 1: responsiveness of numerator less thanchange in denominator
• Perfectly inelastic, |E | = 0: no change in numerator forchange in denominator
• Perfectly elastic, |E | =∞: infinite change in numerator forchange in denominator
Admin RFH Curves E & Policy Elasticities Paper Recap
Useful Elasticity Terms
• Unit elastic, |E | = 1: any percent changes in prices areequally matched by percent changes in Q
• Elastic, ∞ > |E | > 1: responsiveness of numerator greaterthan change in denominator
• Inelastic, 0 < |E | < 1: responsiveness of numerator less thanchange in denominator
• Perfectly inelastic, |E | = 0: no change in numerator forchange in denominator
• Perfectly elastic, |E | =∞: infinite change in numerator forchange in denominator
Admin RFH Curves E & Policy Elasticities Paper Recap
Useful Elasticity Terms
• Unit elastic, |E | = 1: any percent changes in prices areequally matched by percent changes in Q
• Elastic, ∞ > |E | > 1: responsiveness of numerator greaterthan change in denominator
• Inelastic, 0 < |E | < 1: responsiveness of numerator less thanchange in denominator
• Perfectly inelastic, |E | = 0: no change in numerator forchange in denominator
• Perfectly elastic, |E | =∞: infinite change in numerator forchange in denominator
Admin RFH Curves E & Policy Elasticities Paper Recap
Useful Elasticity Terms
• Unit elastic, |E | = 1: any percent changes in prices areequally matched by percent changes in Q
• Elastic, ∞ > |E | > 1: responsiveness of numerator greaterthan change in denominator
• Inelastic, 0 < |E | < 1: responsiveness of numerator less thanchange in denominator
• Perfectly inelastic, |E | = 0: no change in numerator forchange in denominator
• Perfectly elastic, |E | =∞: infinite change in numerator forchange in denominator
Admin RFH Curves E & Policy Elasticities Paper Recap
Income Elasticity of Demand
• We are interested in the income elasticity of demand
EDI =
%∆QD
%∆I
• What do you consume more of as your income increases?
These are normal goods, and E > 0 (but E ≤ 1)
• What do you consume less of as your income increases?These are inferior goods, and E < 0.
• What does mean if EDI > 1 Your consumption increases more
than your income → luxury good
Admin RFH Curves E & Policy Elasticities Paper Recap
Income Elasticity of Demand
• We are interested in the income elasticity of demand
EDI =
%∆QD
%∆I
• What do you consume more of as your income increases?These are normal goods, and E > 0 (but E ≤ 1)
• What do you consume less of as your income increases?
These are inferior goods, and E < 0.
• What does mean if EDI > 1 Your consumption increases more
than your income → luxury good
Admin RFH Curves E & Policy Elasticities Paper Recap
Income Elasticity of Demand
• We are interested in the income elasticity of demand
EDI =
%∆QD
%∆I
• What do you consume more of as your income increases?These are normal goods, and E > 0 (but E ≤ 1)
• What do you consume less of as your income increases?These are inferior goods, and E < 0.
• What does mean if EDI > 1
Your consumption increases morethan your income → luxury good
Admin RFH Curves E & Policy Elasticities Paper Recap
Income Elasticity of Demand
• We are interested in the income elasticity of demand
EDI =
%∆QD
%∆I
• What do you consume more of as your income increases?These are normal goods, and E > 0 (but E ≤ 1)
• What do you consume less of as your income increases?These are inferior goods, and E < 0.
• What does mean if EDI > 1 Your consumption increases more
than your income → luxury good
Admin RFH Curves E & Policy Elasticities Paper Recap
Contemplate Yourself!
With your neighbor, think of some examples
• What is the sign of the income elasticity of demand for freshfruit and vegetable consumption?
• Give an example of a normal good and an inferior good
Admin RFH Curves E & Policy Elasticities Paper Recap
Cross-Price Elasticity of Demand
How much does your demand for pluots change when the price ofapricots increases?
EDXY =
%∆QDX
%∆PY
• The responsiveness of quantity demanded of good X to priceof good Y
• If EDXY is positive, are X and Y substitutes or complements?
Policy examples, please!
Admin RFH Curves E & Policy Elasticities Paper Recap
Cross-Price Elasticity of Demand
How much does your demand for pluots change when the price ofapricots increases?
EDXY =
%∆QDX
%∆PY
• The responsiveness of quantity demanded of good X to priceof good Y
• If EDXY is positive, are X and Y substitutes or complements?
Policy examples, please!
Admin RFH Curves E & Policy Elasticities Paper Recap
Cross-Price Elasticity of Demand
How much does your demand for pluots change when the price ofapricots increases?
EDXY =
%∆QDX
%∆PY
• The responsiveness of quantity demanded of good X to priceof good Y
• If EDXY is positive, are X and Y substitutes or complements?
Policy examples, please!
Admin RFH Curves E & Policy Elasticities Paper Recap
Paper Overview
• Handout also posted online
Admin RFH Curves E & Policy Elasticities Paper Recap
What We Did This Class
1. Non-linear demand curves
2. Elasticity and policy
3. Many kinds of elasticity
4. Paper assignment
Admin RFH Curves E & Policy Elasticities Paper Recap
Next Class
• Turn in Problem Set 3
• GLS, Chapter 4