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Elasticity. AP Economics Mr. Bordelon. Why is the demand curve sloped negatively?.

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elasticity

Elasticity

AP Economics

Mr. Bordelon

why is the demand curve sloped negatively
Why is the demand curvesloped negatively?
  • Substitution effect. The substitution effect of a change in the price of a good is the change in the quantity demanded of that good as the consumer substitutes the good that has become relatively cheaper for the good that has become relatively more expensive.
    • When the price of one increases, a substitute will look more attractive. Consumer will buy less of the original good.
why is the demand curve sloped negatively1
Why is the demand curvesloped negatively?
  • Income effect. The income effect of a change in the price of a good is the change in the quantity of that good deamanded that results from a change in the consumer’s purchasing power when the price of the good changes.
    • In this case, think of income not as a sum of money, but what you can actually buy with that sum. This “purchasing power” is referred to as real income.
why is the demand curve negatively sloped
Why is the demand curvenegatively sloped?
  • Normal goods. Goods for which demand decreases when income falls.
  • Inferior goods. Goods for which demand increases when income falls.
why is the demand curve sloped negatively2
Why is the demand curvesloped negatively?
  • For the majority of g/s, income effect is not important and has no significant effect on individual consumption.
  • When the income effect matters, it reinforces the substitution effect.
    • When the price of a g/s absorbs a substantial share of income, consumers of that good become poorer because real income falls.
    • Reduction in income leads to reduction in Qd and reinforces substitution effect.
why is the demand curve sloped negatively3
Why is the demand curvesloped negatively?
  • How does this affect the demand for normal goods?
  • How does this affect the demand for inferior goods?
what is elasticity
What is elasticity?
  • Elasticity. Measures the responsiveness of one variable to changes in another.
  • Price elasticity of demand. Ratio of the percent change in Qd to percent change in P along the demand curve.
slide10
Hmmm...
  • Law of demand states that P and Qd will always move in opposite directions.
    • A positive %ΔP (a rise in price) leads to a negative %ΔQd.
    • A negative %ΔP (a fall in price) leads to a positive %ΔQd.
  • So what’s the problem?
why do we use the midpoint method
Why do we usethe midpoint method?
  • Suppose you have to measure the price elasticity of demand for steak in two different countries.
    • Steak in the United States tends to be cheaper than in Germany because of taxes. Steak in the U.S. is $5/pound. Steak in Germany is $10/pound.
    • Steak between Germany and the U.S. is 100% higher. Steak between the U.S. and Germany is 50% cheaper.
    • If you calculate it like this, you end up with two different elasticities.
how do i interpret elasticity
How do I interpret elasticity?
  • Perfectly inelastic
    • Price elasticity is = 0.25.
      • Ed = %ΔQd/% ΔP = 0.25.
    • Assume for a second that price increased by 1%. What can we predict about Qd, given that Ed = 0.25?
how do i interpret elasticity1
How do I interpret elasticity?
  • Perfectly inelastic
    • Price elasticity is = 0.25. Ed = %ΔQd/% ΔP = 0.25.
    • Assume for a second that price increased by 1%. What can we predict about Qd, given that Ed = 0.25?
      • Qd will decrease by only 0.25%. Why?
    • Now, what would be the smallest response possible to a price increase?
how do i interpret elasticity2
How do I interpret elasticity?
  • Perfectly inelastic
    • None, or rather 0. Ed = 0%/1% = 0.
    • A product that is perfectly inelastic has an elasticity of demand of 0, meaning that Qd does not respond at all to a change in price.
      • When the demand is perfectly inelastic, the demand curve is a vertical line.
how do i interpret elasticity3
How do I interpret elasticity?
  • Perfectly inelastic
    • Assume that price elasticity is 10.
      • Ed = %ΔQd/%ΔP = 10
    • Assume that P increases by 1%. If Ed = % ΔQd/1% =10, what can we predict about Qd?
how do i interpret elasticity4
How do I interpret elasticity?
  • Perfectly inelastic
    • Assume that price elasticity is 10.
      • Ed = % ΔQd/% ΔP = 10
    • Assume that P increases by 1%. If Ed = % ΔQd/1% =10, what can we predict about Qd?
      • Qd will decrease by 10%.
    • What would be the largest response to a price increase?
how do i interpret elasticity5
How do I interpret elasticity?
  • Perfectly inelastic
    • Consumers immediately reduce consumption to 0.
    • Ed = 0
how do i interpret elasticity6
How do I interpret elasticity?
  • Perfectly elastic
    • What would be the largest response to a price decrease?
how do i interpret elasticity7
How do I interpret elasticity?
  • Perfectly elastic
    • What would be the largest response to a price decrease?
    • Consumers immediately increase consumption to an infinitely large amount.
      • If price increased 1%, and an enormous change to Qd, then %ΔQd = ∞.
      • So in that case, Ed = ∞.
how do i interpret elasticity8
How do I interpret elasticity?

Perfectly elastic. Ed = ∞

perfectly elastic and inelastic
(Perfectly) Elastic and Inelastic
  • If a demand curve is closer to vertical (steeper), then this tends to be inelastic.
  • If a demand curve is closer to horizontal (flatter), then this tends to be elastic.
elastic inelastic unit elastic
Elastic, Inelastic, Unit Elastic
  • Elastic. Ed > 1
  • Inelastic. Ed < 1
  • Unit elastic. Ed = 1
who cares
Who cares?
  • Ashley asks, “Bordelon, thanks for sharing all this crap about elasticity, but honestly, who cares? Who cares, Bordelon? Why are you doing this to us? Why? WHY?!?”
businesses care ashley
Businesses Care, Ashley
  • Total Revenue. Total value of sales of a good or service. Total revenue is equal to price multiplied by quantity sold.
    • TR = (P)(Q sold)
  • “Great Bordelon, but that doesn’t answer my question.”
  • “No, I guess it doesn’t Ashley. I should be ashamed of myself.”
psych
Psych
  • Actually, Ed affects how businesses set price.
  • Suppose a business wants to increase TR by increasing price. What can we expect to happen? (Hint: think law of demand!)
psych1
Psych
  • Actually, Ed affects how businesses set price.
  • Suppose a business wants to increase TR by increasing price. What can we expect to happen? (Hint: think law of demand!)
    • As the price increases, the quantity demanded will decrease.
    • Well, this affects TR. Up, down or remain the same?
total revenue and elasticity
Total Revenue and Elasticity
  • Ultimately, the effect on TR depends on which is stronger, higher price or lower quantity.
    • Price effect. After a price increase, each unit sold sells at a higher price, which tends to raise revenue.
    • Quantity effect. After a price increase, fewer units are sold, which tends to lower revenue.
total revenue and elasticity1
Total Revenue and Elasticity
  • P increases by 1%, Qd decreases by 5%. Identify elasticity.
total revenue and elasticity2
Total Revenue and Elasticity
  • P increases by 1%, Qd decreases by 5%. Elastic.
    • TR decreases because decrease in quantity is stronger than increase in price.
total revenue and elasticity3
Total Revenue and Elasticity
  • P increases 10%, Qd decreases 5%. Identify elasticity.
total revenue and elasticity4
Total Revenue and Elasticity
  • P increases 10%, Qd decreases 5%. Inelastic.
    • TR increases because decrease in quantity is weaker than increase in price.
total revenue and elasticity5
Total Revenue and Elasticity
  • P increases by 10%, Qd decreases 10%. Identify elasticity.
total revenue and elasticity6
Total Revenue and Elasticity
  • P increases by 10%, Qd decreases 10%. Unit elastic.
    • TR will not change because decrease in quantity is equal to increase in price.
total revenue and elasticity7
Total Revenue and Elasticity
  • Suppose initial price of slices of pizza is $2 and 50 slices are sold every day (point A). Calculate total revenue.
    • TR = PQ
total revenue and elasticity8
Total Revenue and Elasticity
  • Suppose initial price of slices of pizza is $2 and 50 slices are sold every day (point A).
    • TR = PQ
    • TR = ($2)(50) = $100
    • Represented by the TR + L rectangle.
total revenue and elasticity9
Total Revenue and Elasticity
  • Assume pizzeria now wishes to increase price to $3 and estimates 40 slices will be sold per day (point B). Calculate total revenue.
total revenue and elasticity10
Total Revenue and Elasticity
  • Assume pizzeria now wishes to increase price to $3 and estimates 40 slices will be sold per day (point B).
    • TR = ($3)(40) = $120
    • Represented by the TR + G rectangle.
total revenue and elasticity11
Total Revenue and Elasticity
  • Area L represents revenue lost due to decreased quantity, loss of $20. Loss of 10 slices at $2 each.
  • Area G represents revenue gained due to increased price, gain of $40 in gained revenue. Gain of 40 slices at $1 extra ($3-$2).
total revenue and elasticity12
Total Revenue and Elasticity
  • $40 - $20 = $20 total revenue increase from higher price.
  • If increased price effect is stronger than downward quantity effect, demand must be inelastic.
  • Converse is also true.
  • Calculate elasticity using midpoint formula.
elasticity along demand curve
Elasticity Along Demand Curve

Calculate remaining elasticities using midpoint formula.

elasticity along demand curve1
Elasticity Along Demand Curve

What happens to total revenue here as price increases?

How does this relate to elastic, inelastic and unit elastic?

factors determining price elasticity of demand
Factors DeterminingPrice Elasticity of Demand
  • Substitutes. The more substitutes, the more elastic the demand. If a product has many substitutes, and the price increases, consumers will have an elastic response because they can easily find alternatives.
  • Necessity vs. Luxury. The less necessary the item, the more elastic the demand. For luxuries, if the price increases, consumers will just do without and have an elastic response.
factors determining price elasticity of demand1
Factors DeterminingPrice Elasticity of Demand
  • Share of income spent on g/s. The larger the expenditure relative to one’s budget, the more elastic the demand, because buyers notice the change in price more. Real income.
  • Time. The longer the time period involved, the more elastic the demand becomes.
questions
Questions
  • There is a 10% rise in the price of bottled water. This creates a 40% change in the quantity demanded. The demand for bottled water is considered to be
    • perfectly inelastic.
    • elastic
    • inelastic
    • perfectly elastic
    • none of the above
questions1
Questions
  • There is a 10% rise in the price of bottled water. This creates a 40% change in the quantity demanded. The demand for bottled water is considered to be
    • perfectly inelastic.
    • elastic
    • inelastic
    • perfectly elastic
    • none of the above
questions2
Questions
  • If a 30% rise in gas prices creates a 0% decrease in the quantity demanded, the demand is said to be
    • inelastic
    • perfectly elastic
    • elastic
    • perfectly inelastic
    • none of the above
questions3
Questions
  • If a 30% rise in gas prices creates a 0% decrease in the quantity demanded, the demand is said to be
    • inelastic
    • perfectly elastic
    • elastic
    • perfectly inelastic
    • none of the above
questions4
Questions
  • All of the following are factors affecting the elasticity of demand EXCEPT
    • availability of substitute goods
    • necessity versus luxury goods
    • how much of a consumer’s budget goes to the good
    • the time horizon in which a change in price is considered
    • the percentage change in the quantity demanded
questions5
Questions
  • All of the following are factors affecting the elasticity of demand EXCEPT
    • availability of substitute goods
    • necessity versus luxury goods
    • how much of a consumer’s budget goes to the good
    • the time horizon in which a change in price is considered
    • the percentage change in the quantity demanded
cross price elasticity of demand
Cross-Price Elasticity of Demand
  • Effect of a change in a product’s price on the quantity demanded for another product.
    • Think complements and substitutes. This elasticity measures how much that demand curve shifts.
cross price elasticity of demand1
Cross-Price Elasticity of Demand
  • Substitutes. If Exy is positive, then X and Y are substitutes.
    • P of Nikes increases 2% and Qd of Converse increases 4%.
    • Econverse,nike = 4%/2% = 2.
cross price elasticity of demand2
Cross-Price Elasticity of Demand
  • Complements. If Exy is negative, then X and Y are complements.
    • P of gasoline increases 20% and Qd of SUVs decreases by 5%.
    • Egas,SUV = -5%/20% = -0.25
cross price elasticity of demand3
Cross-Price Elasticity of Demand
  • Unrelated products. If Exy = 0, then X and Y are unrelated products.
    • If P of Cinnamon Toast Crunch increased, it’s a good bet there would be no impact on the quantity demanded of New Orleans Saints season tickets.
income elasticity of demand
Income Elasticity of Demand
  • Percentage change in quantity demanded which results from some percentage change in consumer incomes.
    • Think changes in income as it relates to demand, particularly normal and inferior goods.
income elasticity of demand1
Income Elasticity of Demand
  • Normal good. Positive income elasticity.
    • American consumer income falls by 2% and quantity of flights to Europe declines by 8%.
    • Ei = 8%/2% = 4.
    • Income-elastic response. True of most goods considered luxuries.
income elasticity of demand2
Income Elasticity of Demand
  • Normal good. Positive income elasticity.
    • Consumer income increases by 4% and quantity of fresh vegetables purchased increases by 1%.
    • Ei = 1%/4% = 0.25
    • Income-inelastic response. Typical for food and other necessities.
income elasticity of demand3
Income Elasticity of Demand
  • Inferior good. Negative income elasticity.
    • Consumer income decreases by 5% and consumers increase consumption of Spam by 4%.
    • Ei = 4%/-5% = -0.80
    • Is there a difference between necessity and luxury when talking about inferior goods?
price elasticity of supply
Price Elasticity of Supply
  • When the price of g/s increases, businesses will increase Qs. Here, we’re concerned with how much quantity will increase in response to the higher price.
price elasticity of supply1
Price Elasticity of Supply

Elastic: Es > 1

Inelastic: Es < 1

Unit elastic: Es = 1

price elasticity of supply2
Price Elasticity of Supply
  • S1 is just a typical supply curve.
  • S2 is a perfectly elastic curve. Even the smallest increase in price would dramatically increase quantity supplied. A small decrease in the price would decrease quantity supplied to zero.
price elasticity of supply3
Price Elasticity of Supply
  • S3 is perfectly inelastic. Even at the highest of prices, there is something that prevents firms from increasing the quantity that they supply.
    • Technology limitation
    • Seasonal
    • Agriculture
factors determining price elasticity of supply
Factors DeterminingPrice Elasticity of Supply
  • Availability of inputs. If a business can get inputs into and out of production quickly, Es will be more elastic. If not, inelastic.
factors determining price elasticity of supply1
Factors DeterminingPrice Elasticity of Supply
  • Time (MOST IMPORTANT).
    • Market period is so short that elasticity of supply is perfectly inelastic (vertical).
    • Short-run supply elasticity is more elastic than market period and depends on ability of producers to respond to price changes as to how elastic it is.
    • Long-run supply elasticity is most elastic because more adjustments can be made over time and quantity can be changed more relative to a small change in price.
factors determining elasticity of supply
Factors DeterminingElasticity of Supply
  • It is July 2010 and the price of oranges is soaring. Farmers would love to supply more oranges at the higher price, but orange crops have already been planted. The quantity of oranges that will be supplied at harvest 2010 (December) was determined months ago during the planting season. The immediate orange supply curve is inelastic or nearly vertical and farmers are incapable of responding to higher price.
factors determining elasticity of supply1
Factors DeterminingElasticity of Supply
  • If high prices continue into early 2011, farmers will plant more acres of oranges next year and supply more oranges. Increase in quantity supplied is greater as more time passes and farmers are able to respond.
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