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Percentages and Elasticity

Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

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Page 1: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Percentages and Elasticity

Page 2: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage: “for each hundred” one per cent: one for each hundred

ex: "I spend ten percent of my income on movies and other forms of entertainment" means that "I spend ten dollars of each hundred dollars of my income on entertainment."

Page 3: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Converting from decimal to percentage notation:

Just move the decimal to the right two places.

.65 65%

Page 4: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

What percentages are equivalent to the following numbers?

(a) .01 1%(b) .94 94%(c) 1.705 170.5%(d) .2386 23.86%(e) .8

80%

Page 5: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Converting from fractions to percentages:

Convert from fraction to decimal by dividing, and then move the decimal to the right two places.

1/4 .25 25%

Page 6: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

What percent of 50 is 10?

20%

4 is what percent of 8?

50%

What percent of 60 is 15?

25%

Questions

Page 7: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Percentage Change:

absolute change = after - before

before before

Page 8: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

If spending increased from $50 to $60, by what percent did spending increase?

percentage change = after - before before

= 60 - 50 50

= 10 / 50 = .20 = 20 %

Page 9: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose your financial aid increased by $50. You used to spend $10 per week on entertainment. You now spend $11. By what percentage did your entertainment spending increase?

percentage change = after - before before

= 11 - 10 10

= 1/10 = .10 = 10 %

Page 10: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Your financial aid is cut back by $50 to its original level. You reduce your entertainment spending from $11.00 back to $10.00. By what percent did your spending decrease?

percentage change = after - before before

= 10 - 11 11

= - 1 / 11 = - .0909 = - 9.09 %

Page 11: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

A positive change indicates an increase.

A negative change indicates a decrease.

Page 12: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

It would be nice to be able to say the following: In response to a $50 increase, you increased your spending by some percent x. In response to a $50 decrease, you decreased your spending by that same x percent. When we get to the concept of elasticity, in particular, we will want to be able to do that.

Page 13: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

average = (before + after) / 2

So we will define percentage changes a little differently. Instead of using our "before" value as our denominator, we will use the average (or midpoint) of our "before" and "after" values as the denominator.

Page 14: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Our percentage change formula becomes

percentage change = after - before average

Page 15: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose your financial aid increased by $50. You increase your spending on entertainment from $10 per week to $11. By what percentage did your entertainment spending increase? (Use the midpoint formula.)

First we need to determine the average of the before and after spending.

average = (before + after) / 2 = (10 + 11) / 2 = (21) / 2 = 10.5

Page 16: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

= after - before average

= 11 - 10 10.5

= 1 / 10.5

= .0952

= 9.52 %

percentage change

Page 17: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Financial aid is cut back by $50. You reduce your spending on entertainment from $11 per week to $10. Using the midpoint formula, determine by what percentage your spending decreases.

percentage change = after - before average

= 10 - 11 10.5

= - 1 / 10.5

= - .0952 = - 9.52 %

Page 18: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose that financial aid for the semester increased from $995 to $1005. Using the midpoint formula, determine by what percent financial aid increased.

percentage change = after - before average

= 1005 - 995 1000

= 10 / 1000 = .01 = 1 %

Page 19: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose the 1% increase in financial aid led you to increase your entertainment budget from $297 to $303. By what percent did you increase your entertainment budget?

percentage change = after - before average

= 303 - 297 300

= 6 / 300 = .02 = 2 %

Page 20: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

In other words, the percentage increase in your entertainment budget was 2 times as large as the percentage increase in financial aid.

This value (2) is the elasticity of your entertainment budget with respect to your financial aid.

fin. aid 1 % ent. budget 2 %

Page 21: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

tells you by what percent X changes when Y changes by 1%.

The elasticity of X with respect to Y

Page 22: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

can be calculated as

the percentage change in X the percentage change in Y.

The elasticity of X with respect to Y

Page 23: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

If in response to a 20% increase in financial aid, you increased your entertainment budget by 40%, what is the elasticity of your entertainment budget with respect to your financial aid?

2

By how much would you expect your entertain- ment budget to increase in response to a 1% increase in financial aid?

2%

Page 24: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose financial aid increased from $1050 to $1100. In response, you increased your entertainment budget from $300 to $320. Calculate the following:

the percentage change in financial aid, the percentage change in your entertainment

budget, and the elasticity of your entertainment budget

with respect to financial aid.

Page 25: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

change in fin. aid = 1100 - 1050 = 50

avg. fin. aid = (1050 + 1100)/2 = 2150/2 = 1075

percentage change in financial aid

= (change in fin. aid) / (avg fin. aid)

= 50 / 1075

= .0465

= 4.65%

percentage change in financial aid

fin. aid: 1050, 1100

Page 26: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

change in ent. budget = 320 - 300 = 20

avg ent. budget = (300 + 320) / 2 = 620/2 = 310

percentage change in entertainment budget

= (change in ent. budget) / (avg ent. budget)

= 20 / 310

= .0645

= 6.45%

percentage change in ent. budget

ent. budget: 300, 320

Page 27: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in entertainment budget percentage change in financial aid

= 6.45/4.65 = 1.387.

So when financial aid increases by1 percent, your entertainment budget

increases by 1.387 percent.

elasticity of entertainment budget

with respect to financial aid

Page 28: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

In the elasticity formula, how do you remember which variable goes on top and which goes underneath?

The cause goes under the line.

CAUSE and UNDER both have a U.

The effect goes on top.

EFFECT and TOP both have a T.

Page 29: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

elasticity = % change in effect

% change in cause

Page 30: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

for our financial aid & entertainment example:

elasticity = % change in .

% change in

Page 31: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Unit Elastic:

|elasticity| = 1

% change in effect

% change in cause = 1

% change in the effect = % change in the cause

Page 32: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

fin. aid 5 % ent. budget 5 %.

Your entertainment budget is unit elastic with respect to financial aid.

Page 33: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Elastic:

|elasticity| > 1

% change in effect

% change in cause > 1

% change in the effect > % change in the cause

Page 34: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

fin. aid 5 % ent. budget 6 %

Your entertainment budget is elastic with respect to financial aid.

Page 35: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Inelastic:

|elasticity| < 1

% change in effect

% change in cause < 1

% change in the effect < % change in the cause

Page 36: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

fin. aid 5 % ent. budget 4 %

Your entertainment budget is inelastic with respect to financial aid.

Page 37: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Price Elasticity of Demand (or Elasticity of Quantity Demanded with

Respect to Price)

measures the responsiveness of consumers' purchases to a change in the price of a commodity.

Page 38: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Notation

means “change” and

% means “percentage change”

examples: Price or P means “change in price”

% P means “percentage change in price”

Page 39: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

the percentage change in the quantity demanded of PCs,

the percentage change in the price of PCs, and the elasticity of demand for PCs with respect

to the price of PCs.

Suppose the price of personal computers increased from $1600 to $1700. As a result, the number of PCs

purchased per week by area consumers dropped from 500 to 400. Calculate the following:

Page 40: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in quantity demanded of PCsquantity: 500, 400

qty demanded of PCs = 400 - 500 = -100

avg qty demanded of PCs = (500 + 400) / 2 = 900 / 2 = 450

% qty demanded of PCs

= ( qty demanded of PCs) / (avg qty demanded)

= -100/450 = -.2222 = - 22.22 %

[The negative indicates a decrease in PCs.]

Page 41: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in price of PCsprice: 1600, 1700

Price of PCs = 1700 - 1600 = 100

avg price = (1600 + 1700) / 2 = 3300 / 2 = $1650

% price of PCs = ( price of PCs) / (avg price)

= 100 / 1650 = .0606 = 6.06 %

Page 42: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price elasticity of demand for PCs

% qty demanded of PCs % price of PCs

= - 22.22 / 6.06 = - 3.667

The negative indicates that there is an inverse relation between the qty demanded of PCs and the price of PCs.

When the price of PCs increases by one percent, the quantity demanded of PCs decreases by 3.667 percent.

Page 43: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

|-3.667| = 3.667 > 1

So, the demand for PCs is elastic with respect to the price of PCs.

Page 44: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

ex: The price elasticity of demand for PCs would be reported as 3.667 instead of -3.667. The negative is understood.

Because it is almost always the case that the qty demanded of a good is inversely related to its price, the negative sign is frequently dropped.

Page 45: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose you have an ailment, for which you must take a particular medication. (Call it Medex.) Every thirty days you purchase one thirty-capsule bottle of Medex. The price of Medex increases from $4 to $5

Medex

per bottle. You still purchase one bottle every thirty days. Calculate the elasticity of your quantity demanded of Medex with respect to the price of Medex.

Page 46: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in price of Medexprice: 4, 5

Price of Medex = 5 - 4 = 1

avg price = (4 + 5)/2 = 9/2 = 4.5

% price of Medex = ( price) / (avg price) = 1 / 4.5 = .2222

So the price of Medex changed by 22.22 %.

Page 47: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty demanded of Medexquantity: 1, 1

qty demanded of Medex = 1 - 1 = 0

avg qty demanded of Medex = (1 + 1) / 2 = 2 / 2 = 1

% qty demanded of Medex

= ( qty demanded) / (avg qty demanded)

= 0 / 1 = 0

So the quantity demanded of Medex changed by 0 %. (It didn’t change at all.)

Page 48: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price elasticity of demand for Medex

% qty demanded of Medex% price of Medex

= 0 / 22.22 = 0

Page 49: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

elasticity = 0

It is a special case of inelastic.

Perfectly Inelastic

Page 50: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose the price of personal computers increases from $1500 to $1700. As a result, the number of

PCs purchased per week by consumers in the area dropped from 850 to 750. Calculate the elasticity of demand for PCs with respect to the price of PCs.

Page 51: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty demanded of PCsquantity: 850, 750

qty demanded of PCs = 750 - 850 = -100

avg qty demanded of PCs = (850 + 750) / 2 = 1600 / 2 = 800

% qty demanded of PCs

= ( qty demanded) / (avg qty demanded)

= -100 / 800 = - .125 = - 12.5 %

Page 52: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in price of PCsprice: 1500, 1700

Price of PCs = 1700 - 1500 = 200

avg price = (1500 +1700) / 2 = 3200 / 2 = 1600

% price of PCs = ( price) / (avg price) = 200 / 1600 = .125 = 12.5%

Page 53: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price elasticity of demand for PCs

% qty demanded of PCs% price of PCs

= -12.5 / 12.5 = -1

Since the absolute value of the elasticity is 1, the quantity demanded of PCs is unit elastic with respect to price.

Page 54: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose you are in the pizza business. As a very small company, you take the area price of pizza ($8) as given. That is, you always charge the same price. The

quantity demanded of your pizza fluctuates. Last week, the quantity demanded of your pizza increased from 750 to 800 pizzas. Calculate the price elasticity of demand for your pizza.

Page 55: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty demanded of pizzaquantity: 750, 800

qty demanded of pizza = 800 - 750 = 50

avg qty demanded of pizza = (750 + 800) / 2 = 1550 / 2 = 775

% qty demanded of pizza

= ( qty demanded) / (avg qty demanded) = 50 / 775 = .0645 = 6.45 %

Page 56: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in price of pizzaprice: 8, 8

Price of pizza = 8 - 8 = 0

avg price = (8 + 8) / 2 = 16 / 2 = 8

% price of pizza = ( price) / (avg price) = 0 / 8 = 0 = 0 %

The price changed by 0 %. (It didn't change at all.)

Page 57: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price elasticity of demand for pizza

% qty demanded of pizza% price of pizza

= 6.45 / 0 = infinity or undefined

Page 58: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

elasticity = infinity

It is a special case of elastic.

Perfectly Elastic or Infinitely Elastic

Page 59: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

1. Elasticity of demand is greater if

there are good substitutes available.

Example: The elasticity of demand for a particular brand of gas would be quite high because there are lots of other brands of gas available.

Determinants of Price Elasticity of Demand

Page 60: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

2. Elasticity of demand is greater if the price of the good is high relative to one’s budget.

Example: The elasticity of demand for a salt is low because salt is a very small part of one’s budget.

Determinants of Price Elasticity of Demand

Page 61: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

3. Elasticity of demand is greater if the product is a luxury rather than a necessity.

Example: The elasticity of demand for insulin by a diabetic is extremely low because insulin is a necessity.

Determinants of Price Elasticity of Demand

Page 62: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

4. Elasticity of demand is greater if the buyer has more time to adjust to a change in price.

Example: The elasticity of demand for gas is more elastic when you allow people more time to adjust. If the price of gas goes up today, you can adjust your consumption only a little bit tomorrow. But if you have a few years, you can replace your car with one that consumes less gas and you can move closer to where you work.

Determinants of Price Elasticity of Demand

Page 63: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Elasticity Graphs

Page 64: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Zero Elasticity or Perfectly Inelastic

Q

P

Page 65: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Low Elasticity (Inelastic)

Q

P

Page 66: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

High Elasticity (Elastic)

Q

P

Page 67: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Infinite Elasticity or Perfectly Elastic

Q

P

Page 68: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Elasticity of a Straight Line

Q

P

at midpoint, |elasticity| = 1

Page 69: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Elasticity of a Straight Line

Q

P above the midpoint,

|elasticity| > 1

Page 70: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Elasticity of a Straight Line

Q

P

below the midpoint, |elasticity| < 1

Page 71: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Elasticity of a Straight Line

Q

P

|elasticity| = 1

|elasticity| > 1

|elasticity| < 1

Page 72: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Constant Elasticity

Q

P

Page 73: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Relationship Between

Price Elasticity of Demand

and Total Revenue

Page 74: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Note: Total Revenue (TR) = Total Expenditure.

Total revenue is from the firm’s perspective; total expenditure is from the consumer’s

perspective. Both are computed by multiplying price by

quantity. Thus,

TR = P Q

Page 75: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Clearly, if both X and Y increase, then the product Z must increase too.

Also, if both X and Y decrease, then the product Z must decrease too.

Consider the product of two numbers,Z = XY.

Page 76: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

That is, if X increases a lot and Y decreases a little, then Z will increase.

If X increases a little and Y decreases a lot, then Z will decrease.

If Y decreases by the same percentage that X increased, then Z will remain unchanged.

However, if X increases and Y decreases, or vice versa, then whether the product Z increases or decreases depends on the relative magnitude of the changes in X and Y.

Page 77: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Generally, when the price of a product increases, the quantity demanded will decrease and vice versa.

So, whether TR increases, decreases, or remains the same when the price of a product changes depends on the relative magnitudes of the changes in price and quantity.

The same idea carries over to the concept of total revenue, which is the product of price and quantity: TR = PQ.

Page 78: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

When Demand is Elastic:

P Q TR

P Q TR

Price and TR move in opposite directions.

Page 79: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Example: Elastic Demand

When the price of PCs increased from $1600 to $1700, the number of PCs decreased from 500 to 400. The elasticity was -3.667.

Initially, TR = (1600)(500) = 800,000.

Later, TR = (1700)(400) = 680,000.

So TR fell when price increased.

Page 80: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

When Demand is Inelastic:

P Q TR

P Q TR

Price and TR move in the same direction.

Page 81: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Example: Inelastic Demand

Suppose when the price of a good increased from $90 to $110, the quantity demanded decreased from 210 to 190. The elasticity can be computed to be -0.5.

Initially, TR = (90)(210) = 18,900.

Later, TR = (110)(190) = 20,900.

So TR increased when price increased.

Page 82: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

When Demand is Unit Elastic:

P Q TR unchanged

P Q TR unchanged

TR is constant.

Page 83: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Example: Unit Elastic Demand

Suppose when the price of personal computers increases from $1500 to $1700, the quantity demanded decreases from 850 to 750. Then the elasticity is -1.

Initially, TR = (1500)(850) = 1,275,000.

Later, TR = (1700)(750) = 1,275,000.

So TR is unchanged when price changes.

Page 84: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Price Elasticity of Supply (or Elasticity of Quantity Supplied with

Respect to Price)

measures the responsiveness of producers to a change in the price of a commodity.

Page 85: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose the price of personal computers increased from $1550 to $1650. As a result, the number of PCs that area manufacturers were willing to produce per week

rose from 490 to 510. Calculate the elasticity of quantity supplied of PCs with respect to the price of PCs.

Page 86: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty supplied of PCsquantity: 490, 510

qty supplied of PCs = 510 - 490 = 20

avg qty supplied of PCs = (490 + 510) / 2 = 1000 / 2 = 500

% qty supplied of PCs

= ( qty supplied) / (avg qty supplied)

= 20 / 500 = .04 = 4 %

Page 87: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in price of PCsprice: 1550, 1650

Price of PCs = 1650 - 1550 = 100

avg price = (1550 +1650) / 2 = 3200 / 2 = $1600

% price of PCs = ( price) / (avg price)

= 100 / 1600 = .0625 = 6.25%

Page 88: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price elasticity of supply of PCs

% qty supplied of PCs % price of PCs

= 4 / 6.25 = .64

When the price of PCs increases by one percent, the quantity supplied of PCs increases by .64 percent.

Since the elasticity is less than one, the quantity supplied of PCs is inelastic with respect to price.

Page 89: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

The Income Elasticity of Demand or Elasticity of Quantity Demanded with

Respect to Income

measures the responsiveness of consumers' purchases to a change in consumer income.

Page 90: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose your income increased from $1000 to $1150 per month. As a result, the number of pounds of potatoes you purchase per

month decreased from 10 to 9. Calculate the elasticity of demand for potatoes with respect to income.

Page 91: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty demanded of potatoesquantity: 10, 9

qty demanded of potatoes = 9 - 10 = - 1

avg qty demanded of potatoes = (10 + 9) / 2 = 19 / 2 = 9.5

% qty demanded of potatoes

= ( qty demanded) / (avg qty demanded)

= - 1 / 9.5 = - .1053 = - 10.53 %

Page 92: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in incomeincome: 1000, 1150

income = 1150 - 1000 = 150

avg income = (1000 +1150)/2 = 2150 / 2 = $1075

% income = ( income) / (avg income)

= 150 / 1075 = .1395 = 13.95 %

Page 93: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

income elasticity of demand for potatoes

% qty demanded of potatoes% income

= - 10.53 / 13.95 = - .75

When the income increases by one percent, the quantity demanded of potatoes decreases by 0.75 percent.

Page 94: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Inferior Good

a good with a negative income elasticity of demand.

The negative sign indicates that income and quantity demanded of the good (potatoes) move in opposite directions. When income rises, people buy less. When income falls, people buy more.

Page 95: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Normal Good

a good with a positive income elasticity of demand.

For normal goods, when income rises, people buy more. When income falls, people buy less. Most goods are normal goods.

Page 96: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose your income increased from $2000 to $2080 per month. As a result, the number of movies you see per month rose from 4 to 5.

Calculate the elasticity of demand for movies with respect to income.

Page 97: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty demanded of moviesquantity: 4, 5

qty demanded of movies = 5 - 4 = 1

avg qty demanded of movies = (4 + 5) / 2 = 9 / 2 = 4.5

% qty demanded of movies

= ( qty demanded) / (avg qty demanded)

= 1 / 4.5 = .2222 = 22.22 %

Page 98: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in incomeincome: 2000, 2080

income = 2080 - 2000 = 80

avg income = (2000 +2080) / 2 = 4080 / 2 = 2040

% income = ( income) / (avg income)

= 80 / 2040 = .0392 = 3.92 %

Page 99: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

income elasticity of demand for movies

% qty demanded of movies% income

= 22.22 / 3.92 = 5.668

When the income increases by one percent, the quantity demanded of movies increases by 5.668 percent.

Since the income elasticity of movies is positive, movies are a normal good.

Page 100: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Cross Elasticity of Demand

measures the responsiveness of the quantity demanded of one good to changes in the price of another good.

Page 101: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose the price of compact diskettes falls from $18 to $14. In response, the quantity demanded of cassettes

demanded of cassettes with respect to the price of CDs.

per week by area consumers falls from 1100 to 900. Calculate the elasticity of the quantity

Page 102: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty demanded of cassettesqty of cassettes: 1100, 900

qty demanded of cassettes = 900-1100 = - 200

avg qty demanded of cassettes = (1100 + 900) / 2 = 2000 / 2 = 1000

% qty demanded of cassettes

= ( qty demanded) / (avg qty demanded)

= - 200 / 1000 = - .20 = - 20 %

Page 103: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in price of CDsCD price: 18, 14

price of CDs = 14 -18 = - 4

avg price of CDs = (18 + 14) / 2 = 32 / 2 = 16

% price of CDs = ( price of CDs) / (avg price of CDs)

= - 4 /16 = - .25 = - 25 %

Page 104: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

cross elasticity of demand for cassettes with respect to the price of CDs

% qty demanded of cassettes% price of CDs

= -20 / -25 = .80

When the price of CDs falls by one percent, the quantity demanded of cassettes falls by .80 percent.

Page 105: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Substitutes

When the cross elasticity between two goods is positive, the two goods are called substitutes.

A substitute is a good that can be used instead of another good.

Page 106: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

When the price of CDs decreases, the quantity demanded of cassettes decreases.

When the price of CDs increases, the quantity demanded of the cassettes increases.

The price of one good and the quantity demanded of the substitute good move in the same direction.

Page 107: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Complements

When the cross elasticity between two goods is negative, the two goods are called complements.

A complement is a good that is used along with another good.

Page 108: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Complements

The price of one good and the quantity demanded of the complementary good move in opposite directions.

When the price of coffee decreases, the quantity demanded of cream increases.

When the price of coffee increases, the quantity demanded of cream decreases.

Page 109: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose the price of CD players increases from $140 to $160. In response, the quantity demanded of CDs per week by area consumers decreases from 1150 to 850. Calculate the cross elasticity of demand for CDs with respect to the price of CD players.

Page 110: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in qty demanded of CDsqty of CDs: 1150, 850

qty demanded of CDs = 850 - 1150 = - 300

avg qty demanded of CDs = (1150 + 850) / 2 = 2000 / 2 = 1000

% qty demanded of CDs

= ( qty demanded) / (avg qty demanded)

= - 300 / 1000 = - .30 = - 30 %

Page 111: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

percentage change in price of CD playersCD player price: 140, 160

price of CD players = 160 -140 = 20

avg price of CD players = (140 + 160) / 2 = 300 / 2 = 150

% price of CD players = ( price) / (avg price)

= 20 / 150 = .1333 = 13.33 %

Page 112: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

cross elasticity of demand for CDs with respect to the price of CD players

% qty demanded of CDs% price of CD players

= - 30 / 13.33 = - 2.25

Since the cross elasticity of demand for CDs with respect to the price of CD players is negative, CDs and CD players are complements.

Page 113: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

The Effect of Elasticity on

the Burden of a Tax

Page 114: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price QD QS

1.09 45 75

1.06 50 70

1.03 55 65

1.00 60 60

.97 65 55

.94 70 50

.91 75 45

Example:

Suppose supply and demand are as shown here. Without a tax, equilibrium price is $1 and equilibrium quantity is 60 units.

Page 115: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

DemandSupply (without tax)

Price

Quantity

$1

60

Example: no tax quantity is 60price is $1

Page 116: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Now suppose a tax of six cents per unit is imposed.

Then, from the buyer’s view, for each quantity supplied, the total price per unit is six cents higher than before.

(Equivalently, for a given total price per unit, suppliers are willing to provide fewer units than before.)

So the buyers see a new supply curve.

Page 117: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

DemandSupply (without tax)

Supply (with tax)Price

Quantity

.06

Page 118: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price QS

1.09 75

1.06 70

1.03 65

1.00 60

.97 55

.94 50

.91 45

Old Supply (no tax):

Page 119: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price QS price (with tax)

1.09 75 1.15

1.06 70 1.12

1.03 65 1.09

1.00 60 1.06

.97 55 1.03

.94 50 1.00

.91 45 .97

Put in the tax.

Page 120: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price QS price (with tax)

1.09 75 1.15

1.06 70 1.12

1.03 65 1.09

1.00 60 1.06

.97 55 1.03

.94 50 1.00

.91 45 .97

new supply as viewed by the buyers:

Page 121: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price QD QS

1.15 75

1.12 70

1.09 45 65

1.06 50 60

1.03 55 55

1.00 60 50

.97 65 45

.94 70

.91 75

If we line up the demand column and our new supply column so that the price columns match, the table looks like this.

Page 122: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

price QD QS

1.15 75

1.12 70

1.09 45 65

1.06 50 60

1.03 55 55

1.00 60 50

.97 65 45

.94 70

.91 75

If we line up the demand column and our new supply column so that the price columns match, the table looks like this.

Equilibrium quantity is now 55. Equilibrium price (from the buyer’s view) is 1.03.

Page 123: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

DemandSupply (without tax)

Supply (with tax)Price

Quantity

1.03

55

.06

tax = .06 Quantity is 55 Buyer pays 1.03

Page 124: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

But the government gets .06.

So the seller gets 1.03 - .06 = .97.

Page 125: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

DemandSupply (without tax)

Supply (with tax)Price

Quantity

1.03

.97

55

.06

tax = .06 Quantity is 55 Buyer pays 1.03 Seller gets 1.03 -.06=.97

Page 126: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

The burden of the tax is shared evenly in this example. The buyer pays three cents more per unit than before the tax and the seller gets three cents less per unit.

Page 127: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Let’s go through the graphs again for the general case of a tax of amount t.

Page 128: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Price

Quantity

Page 129: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Price

Quantity

P0

Q0

Before tax:quantity is Q0 price is P0

Page 130: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Supply (with tax)Price

Quantity

P0

Q0

t

Page 131: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Supply (with tax)Price

Quantity

Pb

P0

Q1 Q0

t

With tax: quantity is Q1

buyer pays Pb

Page 132: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Supply (with tax)Price

Quantity

Pb

P0

Ps

Q1 Q0

t

With tax: seller gets Ps = Pb - t

Page 133: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

With the tax, the buyer pays more and the seller receives less than without the tax. The burden of the tax is shared.

Page 134: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Suppose the elasticity of demand is smaller.

The demand curve is steeper.

How does this affect how the tax burden is divided?

Page 135: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Price

Quantity

P0

Q0

Page 136: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Supply (with tax)

Price

Quantity

1.04

1.00 .98

59 60

.06

tax = .06 Quantity is 59 Buyer pays 1.04 Seller gets 1.04 -.06=.98Consumer bears greater share of tax burden.

Page 137: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

When demand is less elastic and consumers are less responsive to price changes, consumers will bear a larger share of the tax burden, and sellers will bear a smaller share.

Page 138: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

In the extreme case where demand is perfectly inelastic (vertical demand curve), consumers will bear the entire burden of the tax.

The price paid by consumers is t dollars more than before the tax. The price received by the seller is the same as before the tax.

Page 139: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand

Supply (without tax)

Supply (with tax)

Price

Quantity

1.06

1.00

60

.06

tax = .06 Quantity is 60 Buyer pays 1.06 Seller gets 1.06 -.06=1.00Consumer bears entire tax burden.

Page 140: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

When supply is less elastic and sellers are less responsive to price changes, sellers will bear a larger share of the tax burden, and buyers will bear a smaller share.

Page 141: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Supply (without tax)

Supply (with tax)Price

Quantity

1.02

1.00

.96

59 60

.06

tax = .06 Quantity is 59 Buyer pays 1.02 Seller gets 1.02 -.06=.96Seller bears greater share of tax burden.

Demand

Page 142: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

In the extreme case where supply is perfectly inelastic (vertical supply curve), sellers will bear the entire burden of the tax.

The price received by sellers is t dollars less than before the tax. The price paid by consumers is the same as before the tax.

Page 143: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

To show this effect on a graph, we need to shift the demand curve instead of the supply curve. From the supplier’s perspective, it seems as if the demand curve has shifted down vertically by the amount of the tax.

Page 144: Percentages and Elasticity. percentage: “for each hundred” one per cent: one for each hundred ex: "I spend ten percent of my income on movies and other

Demand (without tax)

Supply Price

Quantity

1.00

.94

60

.06

tax = .06 Quantity is 60Seller gets .94 Buyer pays .94 + .06 = 1.00Seller bears entire tax burden.

Demand (with tax)