Consumer Behavior Ch. 7
Consumer Behavior
Ch. 7
The Budget Line
The budget line depicts the consumption “bundles” that a consumer can afford. People consume less than they desire because their
spending is constrained, or limited, by their income.
The Consumer’s Budget Line...
Quantityof Pizza
Quantityof Pepsi
0
250
50 100
500 B
C
A
Consumer’sBudget line
The Consumer’s Budget Line
The slope of the budget line equals the relative price of the two goods, that is, the price of one good compared to the price of the other.
It measures the rate at which the consumer will trade one good for the other.
Preferences: What the Consumer Wants
A consumer’s preference among consumption bundles may be illustrated with indifference curves.
An indifference curve shows bundles of goods that make the consumer equally happy.
The Consumer’s Preferences...
Quantityof Pizza
Quantityof Pepsi
0
C
B
A Indifferencecurve, I1
D
I2
The consumer is indifferent, or equally happy, with the combinations shown at points A, B, and C because they are all on the same curve.
The Consumer’s Preferences
The Marginal Rate of Substitution
The slope at any point on an indifference curve is the marginal rate of substitution. It is the rate at which a consumer is willing to substitute one good for
another. It is the amount of one good that a consumer requires as compensation to
give up one unit of the other good.
The Consumer’s Preferences...
Quantityof Pizza
Quantityof Pepsi
0
C
B
A
D
Indifferencecurve, I1
I21MRS
Properties of Indifference Curves
Higher indifference curves are preferred to lower ones.
Indifference curves are downward sloping.
Indifference curves do not cross.Indifference curves are bowed
inward.
Property 1: Higher indifference curves are preferred to lower ones.
Consumers usually prefer more of something to less of it.
Higher indifference curves represent larger quantities of goods than do lower indifference curves.
Property 2: Indifference curves are downward sloping.
A consumer is willing to give up one good only if he or she gets more of the other good in order to remain equally happy.
If the quantity of one good is reduced, the quantity of the other good must increase.
For this reason, most indifference curves slope downward.
Property 3: Indifference curves do not cross.
Quantityof Pizza
Quantityof Pepsi
0
C
A
B
1MRS = 1
8
3
Indifferencecurve
A
Property 4: Indifference curves are bowed inward.
Quantityof Pizza
Quantityof Pepsi
0
14
2
3
7
B
1
MRS = 6
4
6
People are more willing to trade away goods that they have in abundance and less willing to trade away goods of which they have little.
Perfect Substitutes
Dimes0
Nickels
21
4
2
I1I2
6
3
I3
Perfect Complements
Right Shoes0
LeftShoes
75
7
5 I1
I2
The Consumer’s Optimum...
Quantityof Pizza
Quantityof Pepsi
0
I1
I2
I3
Budget constraint
AB
Optimum
How Changes in Income Affect the Consumer’s Choices
An increase in income shifts the budget line outward. The consumer is able to choose a better combination of goods
on a higher indifference curve.
An Increase in Income...
Quantityof Pizza
Quantityof Pepsi
0
I1
I2
2. …raising pizza consumption…
3. …and Pepsiconsumption.
Initial optimum
New budget line
1. An increase in income shifts the budget line outward…
Initial budget line
New optimum
How Changes in Prices Affect Consumer Choices
A fall in the price of any good rotates the budget constraint outward and changes the slope of the budget line.
A Change in Price...
Quantity of Pizza100
Quantity of Pepsi
1,000
500
0
I1
New budget constraint
3. …and raising Pepsiconsumption.
Initial budget constraint
2. …reducing pizza consumption…
1. A fall in the price of Pepsi rotates the budget constraint outward…
New optimum
I2
Harcourt, Inc. items and derived items copyright © 2001 by Harcourt, Inc.
Income and Substitution Effects A price change has two effects on
consumption. An income effect A substitution effect
The income effect is the change in consumption that results when a price change moves the consumer to a higher or lower indifference curve.
The substitution effect is the change in consumption that results when a price change moves the consumer along an indifference curve to a point with a different marginal rate of substitution.
X2
X1
Eb
I1
I2
xa xb
Ea
The new optimum is Eb on I2.
The Total Price Effect is xa to xb
X2
X1
I1
I2
xa xb
EaEb
Draw a line parallel to the new budget line and tangent to the old indifference curve
X2
X1
Ec I1
I2
xa xc xb
EaEb
The new optimum on I1 is at Ec. The movement from
Ea to Ec (the increase in quantity demanded from
Xa to Xc) is solely in response to a change in
relative prices
X2
X1
I1
I2
Substitution Effect
EaEb
Ec
This is the substitution effect.
Xa Xc
A Change in Price: Substitution Effect
The substituiton effect increases the quantity demanded of a good whose price has fallen and reduces the quantity demanded of a good whose price has risen.
A Change in Price: Income Effect
The income effect leads consumers to buy more of a product whose price has fallen, if it is a normal good.
Because of the combined operation of the income and substitution effects, the demand curve for any normal good will be negatively sloped.