1. Chapter 6
Consumer Choice and Demand

2. Utility Analysis
• The utility or satisfaction, you derive from
consumption of a good or service.
– It cannot be compared with another person’s
experience.

3. Tastes and Preferences
• Utility: the sense of pleasure or satisfaction.
– It is subjective.
– It depends on YOUR taste and preferences.
– Assumption that tastes are given and relatively
stable.

4. The Law of Diminishing Marginal
Utility
• Total utility- the total satisfaction you derive
from consumption.
• Marginal utility- the change in total utility
resulting from a one-unit change in
consumption.

5. The Law of Diminishing Marginal
Utility
 The more of a good consumed
 The smaller the increase in total utility
 Marginal utility from each additional unit
 Declines as more is consumed
 Disutility
 Negative marginal utility
 “Been there; done that”

6. Measuring Utility
• Units of Utility
– It is more details on how much you enjoyed your
consumption.
• Each person has a uniquely subjective utility
scale.

7. LO2
Utility Derived from Drinking
Water After Jogging Four Miles
Exhibit 1

8. LO2 Exhibit 2
Total Utility and Marginal Utility You Derive from
Drinking Water after Jogging Four Miles
(a) Total utility (b) Marginal utility
80
Marginal utility
Total utility
60
40
40
20
20
0
0 1 2 3 4 5 1 2 3 4 5
Glasses (8-ounce) Glasses (8-ounce)
Total utility increases with each of the
first 4 glasses of water consumed but Marginal utility declines
by smaller and smaller amounts MU of the 5th glass is negative
The 5th glass causes TU to fall

9. Utility Maximization in a World
without Scarcity
• Free good
– Increase consumption as long as marginal utility is
positive.
• What if there are two goods?
– Consume until the marginal utility of each is zero.

10. LO2 Exhibit 3
Total and Marginal Utilities from
Pizza and Videos

11. Utility Maximization in a World of
Scarcity
• Goods are not free
• Limited income now
– What do we do?
• We find an equilibrium.

12. Utility Maximizing Conditions
• Once a consumer is in equilibrium there is no
way to increase utility by reallocating the
budget.
• Consumer equilibrium is achieved when the
budget is exhausted and the last dollar spent
on each good yields the same MU.
– The consumer gets the same bang from the last
buck spent on each good.

13. Utility Maximizing Conditions
MU x MU y
=
px py

14. Example of Consumer
Equilibrium

15. Consumer Surplus
– Value of a good purchased must at least
equal the Price
 Demand curve
– Marginal valuation
 Consumer surplus
– Consumer bonus
– Value of total utility minus total spending
– Area under Demand curve, above Price

16. LO3 Exhibit 6
Consumer Surplus from Sub Sandwiches
$8 At P=$4:
•1st sub valued at $7
7
Price per subs
•2nd sub valued at $6
6
•3rd sub valued at $5
5 •4th sub valued at $4
4 •Willing to pay $22 for 4 subs
3 •Pays only $16 for 4 subs
2 •Consumer surplus
1 $22-$16 = $6
D
0 1 2 3 4 5 6 7 8 Subs per
month
When P drops to $3, consumer surplus increases by $4

17. Market Demand and Consumer
Surplus
 Market Demand curve
– Horizontal sum of individual Demand curves
– Total quantity demanded, per period, by all
consumers, at various prices
 Consumer surplus for the market
– Amount consumers are willing to pay minus amount
they pay
– Net benefit for consumers
– Economic welfare

18. LO3 Exhibit 7
Summing Individual Demand Curves to Derive
Market Demand for Sub Sandwiches
(a) You (b) Brittany (c) Chris (d) Market demand
for subs
$6 $6 $6 $6
Price
4 4 4 4 dY+dB+dC=D
2 2 2 2
dY dB dC
0 2 4 6 0 2 4 0 2 0 2 6 12
Subs per month
Market demand curve is the horizontal sum of individual demand curves

19. LO3 Market Demand and
Consumers Surplus
Consumer surplus at a price of $2
Exhibit 8
is shown by the blue area.
Price per unit
If the price falls to $1, consumer
surplus increases to include the
green area.
At a zero price, consumer surplus
increases to the entire area under
the D curve.
$2
1 D
0 Quantity per period

20. Role of Time in Demand
 Consumption
– Money price
– Time price
 Willing to pay premium for time-saving goods