Chapter 10 — Front Matter
Purpose and Overview
Every day, people make dozens of economic choices without thinking of them as economic choices. You decide what to eat for breakfast. You choose whether to spend an hour studying or watching a show. You pick one brand of shampoo over another. You stop eating pizza after the third slice even though the first was wonderful.
Each of these decisions has something in common: you are a consumer with limited resources — money, time, and energy — making choices among alternatives. This chapter introduces consumer choice, the study of how individuals allocate their limited budgets among competing goods and services. We examine what economists mean by utility, how satisfaction changes as you consume more of something, how prices and income constrain what you can buy, and how consumers respond when prices or incomes change. We also introduce consumer surplus and take an honest look at where the standard model of consumer choice is useful and where it falls short.
The goal of this chapter is not to build a calculus-based theory of rational behavior. It is to give you a set of ideas and tools that help explain observable patterns in consumer behavior — patterns you can recognize in your own life and in real markets.
Opening Question
Think about the last thing you bought that you did not strictly need. Why did you stop at one, or two, or three? What is the most you would have paid rather than go without it — and how does that compare to what you actually paid? By the end of this chapter, you will have precise language and tools for answering questions like these.
9Sections
15Key Terms
3Worked Examples
39Practice Items
Learning Objectives
- 1Explain the basic problem every consumer faces and the factors that shape consumer choices.
- 2Define utility and distinguish total utility from marginal utility.
- 3Calculate marginal utility from a total utility table and state the law of diminishing marginal utility.
- 4Explain why diminishing marginal utility helps explain downward-sloping demand and diversified consumption.
- 5Construct a budget constraint and explain how income and price changes affect it.
- 6Distinguish the substitution effect from the income effect and connect both to the law of demand.
- 7Define consumer surplus, calculate it numerically and graphically, and explain why it matters for policy.
- 8Identify behavioral limits on consumer choice, including bounded rationality, framing, loss aversion, present bias, and defaults.
- 9Apply consumer choice concepts to real-world purchasing decisions, firm pricing strategies, and public policy.
Sections 10.1 – 10.4
Utility, Marginal Thinking, and Diminishing Returns
Consumers and Choices · Utility · Marginal Utility · Diminishing Marginal Utility
Section 10.1
Consumers and Choices
In economics, a consumer is any individual, household, or organization that purchases goods and services to satisfy wants or needs. When you buy a sandwich, you are a consumer. When a family pays rent, they are consumers. When a school purchases textbooks, it acts as a consumer.
Consumer behavior is one of the foundational subjects of microeconomics. If we want to understand why demand curves slope downward, why a price increase causes people to buy less, why some goods are close substitutes while others are not, and why total revenue rises or falls when a price changes, we need a model of how consumers think and choose.
The Basic Problem Every Consumer Faces
Wants and desires are large, sometimes unlimited. Resources — primarily income and time — are limited. Goods and services have prices. A consumer must choose what to buy and what to go without.
This is scarcity applied to an individual. The consumer cannot have everything, so she must make tradeoffs. The study of consumer choice is the study of how those tradeoffs are made.
| Factor | Description |
|---|
| Preferences | What the consumer likes and dislikes, how strongly she prefers one good over another, and how willing she is to substitute one thing for another |
| Prices | The cost of each good relative to others; when prices change, consumers typically adjust what they buy |
| Income | The total resources available to spend; a higher income expands choices, a lower income restricts them |
| Information | What the consumer knows or believes about the goods available (returns in Chapter 17) |
| Norms, habits, and context | Behavioral and situational influences on choice (Section 10.8) |
Positive and Normative Questions About Consumer Choice
A positive question asks what consumers do and why: Why do people buy more of something when its price falls? A normative question asks what consumers should do: Should people save more? Economics largely sets normative questions aside and focuses on explaining behavior. This chapter follows that approach.
- Explain, in your own words, why scarcity applies to consumers just as it applies to societies.
- List the five factors that shape consumer decisions. Choose one and explain how a change in it would affect your own recent purchases.
- Write one positive question and one normative question about consumer spending on transportation.
Section 10.2
Utility and Satisfaction
Economists use the concept of utility to represent the satisfaction, pleasure, or benefit a consumer receives from consuming a good or service. Utility is a mental concept, not a physical quantity. You cannot place it on a scale or measure it in grams. However, we can make useful comparisons: you can say you prefer one combination of goods to another, you can say you would give up some of one good to get more of another, and you can identify whether consuming more of something increases or decreases your satisfaction.
| Concept | Description |
|---|
| Cardinal utility | Imagines satisfaction can be measured in precise numerical units ("utils"); makes the math clean but requires unrealistic precision |
| Ordinal utility | Only requires that consumers can rank alternatives — A preferred to B, B preferred to C — without saying exactly how much more |
| Total utility | The overall satisfaction from all units of a good consumed; typically rises as consumption increases, at least up to a point |
Why Ordinal Utility Is Enough
For this textbook, we use utility mainly as a framework for reasoning, not as a precise calculation. The most important ideas — diminishing marginal utility, budget constraints, and consumer surplus — do not require exact numbers to be understood.
- Explain the difference between ordinal and cardinal utility in one or two sentences each.
- Why might economists prefer ordinal utility for building general theories of consumer behavior?
- Give an example from your own life where total utility kept rising, even though each additional unit added a little less satisfaction than the one before.
Section 10.3
Marginal Utility
In economics, the word marginal always means "additional" or "at the edge of current choices." Marginal utility is the additional satisfaction gained from consuming one more unit of a good. Consumers rarely face all-or-nothing choices. They ask not "Should I eat pizza or not?" but "Should I eat one more slice?"
The Marginal Utility Formula
Marginal Utility = Change in Total Utility ÷ Change in Quantity
MU = ΔTU ÷ ΔQ
| Slices of Pizza | Total Utility (utils) | Marginal Utility (utils) |
|---|
| 0 | 0 | — |
| 1 | 30 | 30 |
| 2 | 55 | 25 |
| 3 | 75 | 20 |
| 4 | 88 | 13 |
| 5 | 95 | 7 |
| 6 | 95 | 0 |
| 7 | 88 | −7 |
Reading the Table Carefully
Total utility rises from 0 to 95 as consumption increases from 0 to 6 slices. Marginal utility starts at 30 and falls steadily. By the sixth slice, marginal utility has fallen to zero. At seven slices, marginal utility is negative — the consumer is made worse off.
- Using the pizza table above, explain what is happening to the consumer's well-being between slice 6 and slice 7.
- If a good's marginal utility table read 50, 40, 40, 30, 10, would this still represent diminishing marginal utility overall? Explain.
- Why does marginal thinking ask "should I have one more?" rather than "should I have this at all?"
Section 10.4
Diminishing Marginal Utility
The law of diminishing marginal utility states that as a consumer consumes additional units of a good, holding other things constant, the marginal utility of each additional unit eventually declines. The first unit of a good tends to satisfy the strongest desire. The second unit adds less satisfaction. The third adds still less. Eventually, more consumption may add nothing at all — or even reduce utility if the consumer is oversatisfied.
This law holds across a remarkable range of goods: the first glass of water when very thirsty provides great relief, while the fifth glass provides very little; the first hour of relaxing television is enjoyable, while the eighth hour in a row becomes numbing.
Why Diminishing Marginal Utility Matters
Three economic implications
- DemandIt helps explain why demand curves slope downward. If each additional unit provides less satisfaction, consumers are only willing to pay less for additional units.
- DiversityIt helps explain diversity in consumption. Because marginal utility falls as you consume more of any one good, consumers spread spending across multiple goods rather than spending everything on one.
- StoppingIt helps explain why consumers stop. Rational consumers stop consuming when the marginal utility of the last unit no longer justifies its cost — the marginal benefit equals marginal cost rule from Chapter 3.
A Caution: Satiation and Exceptions
Diminishing marginal utility is a strong pattern, but not an absolute universal. Some experiences produce increasing marginal utility over a range — learning a skill, collecting items in a set, or building a habit. Utility also depends heavily on context: a single piece of chocolate on an ordinary day provides less marginal utility than a piece of chocolate after a long period without sweets.
- State the law of diminishing marginal utility in one sentence.
- Give an example from daily life not used in this section.
- Explain how diminishing marginal utility connects to the law of demand.
- Explain how diminishing marginal utility connects to consumption diversity.
- Describe a situation where increasing marginal utility might hold over some range.
- Why does context (such as how recently you consumed a good) affect marginal utility?
Sections 10.5 – 10.7
Budgets, Substitution, and the Benefits of Exchange
Budget Constraints · Substitution and Income Effects · Consumer Surplus
Section 10.5
Prices, Income, and Budget Constraints
Utility theory tells us how consumers rank alternatives. But consumers are not free to choose any combination they like — they are constrained by their income and by the prices of goods. This is captured by the budget constraint: all the combinations of goods a consumer can purchase given a fixed income and fixed prices. Any combination the consumer can afford lies on or inside the budget constraint. Any combination that costs more than the consumer's income is unattainable.
Suppose a student has $30 per week to spend on streaming subscriptions ($10 each) and books ($5 each).
| Streaming Subscriptions | Books | Total Spending |
|---|
| 3 | 0 | $30 |
| 2 | 2 | $30 |
| 1 | 4 | $30 |
| 0 | 6 | $30 |
Plotted with subscriptions on one axis and books on the other, these combinations form the budget line. Any point on the line is exactly affordable. Any point inside (below and to the left) is affordable with money left over. Any point outside (above and to the right) is unaffordable. The slope of the budget line reflects the relative prices of the two goods.
| Change | Effect on the Budget Line |
|---|
| Income increases | The budget line shifts outward, parallel to the original. The consumer can afford more of both goods. The slope does not change because relative prices are unchanged. |
| Income decreases | The budget line shifts inward, parallel to the original. |
| Price of one good falls | The budget line rotates outward along that good's axis, while the other intercept stays fixed. The slope becomes flatter (relative to that axis). |
| Price of one good rises | The budget line rotates inward along that good's axis, while the other intercept stays fixed. |
Common Misconception
A price change does not shift the budget line in parallel — it rotates it, because only one good becomes relatively cheaper or more expensive. Only a change in income produces a parallel shift.
- A consumer has $40 to spend on coffee ($4) and pastries ($2). Find both intercepts and the slope of the budget line.
- If the consumer's income rises to $60, what happens to each intercept? Does the slope change?
- If the price of pastries falls to $1, which intercept changes? What happens to the slope?
Section 10.6
Substitution and Choice
When a price changes, a consumer's behavior shifts for two related reasons: the substitution effect and the income effect.
| Effect | Description | Example |
|---|
| Substitution effect | Occurs because a price change makes one good relatively more or less expensive than alternatives; consumers shift toward the relatively cheaper good | Bus fare rises, subway fare stays the same; commuters shift toward the subway |
| Income effect | Occurs because a price change affects real purchasing power, even if nominal income is unchanged | A fall in the price of a good you buy regularly makes your income go further, as if income had risen |
For most goods, an increase in real income leads people to buy more — these are normal goods. For some goods, higher income leads people to buy less, perhaps because they can now afford superior substitutes — these are inferior goods (not a value judgment, just a term). We revisit this distinction in Chapter 15.
Why Demand Curves Slope Downward
1. When a price falls, the good becomes relatively cheaper, so consumers substitute toward it (substitution effect).
2. When a price falls, real income rises, and consumers generally buy more of most goods (income effect).
Both effects typically push in the same direction for most goods: lower price, higher quantity demanded.
Substitutes and Elasticity
The strength of the substitution effect depends on how many close substitutes are available. Goods with many close substitutes tend to have more elastic demand (Chapter 9); goods with few substitutes tend to have inelastic demand.
- Define the substitution effect in your own words.
- Define the income effect in your own words.
- Give an example of a normal good and explain why.
- Give an example of a possible inferior good and explain why.
- Explain why both effects usually push demand in the same direction.
- Explain how the number of close substitutes affects the size of the substitution effect.
Section 10.7
Consumer Surplus at an Introductory Level
When a consumer buys a good, she often values it more than she pays for it. The difference between what she would have been willing to pay and what she actually pays is her consumer surplus — the net benefit she receives from participating in a market transaction.
Example 10.7.1
A simple consumer surplus calculation
- SituationAmara is deciding whether to buy a used bicycle. The maximum price she would pay is $200. She finds one priced at $130.
- CalculationConsumer surplus = $200 − $130 = $70
- MeaningShe gains $70 worth of value beyond what she paid. If the price had been exactly $200, she would have been indifferent — no surplus. Above $200, she would not have bought it at all.
Key takeaway: Consumer surplus is the value a consumer keeps, not a cash payment.
Consumer surplus can be illustrated graphically using the demand curve, which shows, for each quantity, the maximum price consumers are willing to pay — the marginal benefit of that unit. The area between the demand curve and the market price (a triangle in a simple linear model) represents total consumer surplus. When prices fall, this triangle grows; when prices rise, it shrinks.
Why Consumer Surplus Matters
Economists use consumer surplus to analyze price controls, taxes, the gains from trade and competition, and the welfare effects of monopoly. We return to it throughout the textbook in these contexts.
- A consumer is willing to pay at most $90 for a service worth that much to her. She pays $65. What is her consumer surplus?
- Explain, using the demand curve, why consumer surplus grows when the market price falls.
- Why is consumer surplus considered a measure of how well markets serve consumers, rather than a measure of how much money changes hands?
Sections 10.8 – 10.9
Behavioral Limits and Real-World Application
Bounded Rationality and Framing · Consumer Choice in Real Life
Section 10.8
Behavioral Limits on Consumer Choice
The consumer choice model rests on several assumptions: consumers have well-defined, stable preferences; they know the prices and qualities of available goods; they make decisions to maximize utility given their budget; and they respond predictably to price and income changes. This model is powerful, but it is a simplification. Behavioral economics — a field that draws on psychology and economics — studies the patterns where real behavior departs from it. Chapter 17 covers this in more depth; we introduce several key ideas here.
| Concept | Description |
|---|
| Bounded rationality | Human reasoning is limited by cognitive capacity, information, and time; consumers use shortcuts, rules of thumb, and habits rather than calculating perfectly |
| Framing effect | The same choice presented differently can lead to different decisions, even when the underlying value is identical ("90% survival rate" vs. "10% mortality rate") |
| Loss aversion | People feel losses more intensely than equivalent gains; losing $50 feels worse than gaining $50 feels good |
| Present bias | The tendency to over-weight immediate costs and benefits relative to future ones — explains undersaving, overconsumption, and difficulty sticking to plans |
| Status quo bias and defaults | People tend to stick with whatever option is currently in place; default settings (such as automatic retirement enrollment) strongly shape outcomes |
Keeping the Standard Model in Perspective
These behavioral insights do not invalidate the standard model. The demand curve still slopes downward, and consumers do respond to prices and income in predictable ways across millions of decisions. Behavioral economics adds precision about where the model's predictions fall short — and how markets and policies might be designed around real human psychology rather than idealized rationality.
- Define bounded rationality.
- Give an original example of a framing effect.
- Explain loss aversion in your own words.
- Describe a situation where present bias affected a decision you or someone you know made.
- Explain why defaults matter so much to outcomes, using the retirement enrollment example or your own.
- Why doesn't behavioral economics overturn the standard model of consumer choice?
Section 10.9
Consumer Choice in Real Life
The tools from this chapter are not only academic. Marginal utility and stopping decisions explain why you stop eating midway through a bag of chips — the marginal utility of another chip is no longer worth the cost. Budget constraints and tradeoffs explain why a family that spends more on housing has less available for food, clothing, and recreation. Substitution in response to price changes explains why commuters switch to public transit when gas prices rise sharply. Consumer surplus explains the value created when a student buys a used textbook for less than she was willing to pay.
How Firms Use Consumer Behavior
Strategies grounded in consumer choice economics
- Quantity discountsFirms offer them because diminishing marginal utility means consumers need lower prices to purchase additional units.
- SubscriptionsSubscription pricing takes advantage of consumers' preference for smooth, predictable spending over variable costs.
- BundlingSelling multiple goods together can capture consumer surplus that individual prices would leave on the table.
- Free trialsFree trials and samples let consumers experience utility before committing to a purchase.
Consumer Choice and Public Policy
Taxes on goods like tobacco and sugar-sweetened beverages raise the price consumers face; how much quantity demanded falls depends on price elasticity, which depends on the availability of substitutes.
Subsidy programs for food, housing, or healthcare aim to help low-income households; understanding budget constraints helps design programs that are effective and efficient.
Consumer protection regulation — truthful labeling, disclosure of interest rates, clear advertising — addresses problems that arise when consumers decide with incomplete or misleading information.
- Describe a real purchase decision where you stopped consuming because the marginal benefit no longer justified the cost.
- Explain why a streaming bundle priced below the sum of its parts might still be profitable for the firm offering it.
- Choose one public policy example (a sin tax, a subsidy, or a disclosure regulation) and explain how it relates to a concept from this chapter.
Chapter 10 — Back Matter
Chapter Summary
- Sec 10.1A consumer is anyone who purchases goods and services to satisfy wants or needs. Every consumer faces scarcity: unlimited wants, limited income and time, and prices that force tradeoffs. Preferences, prices, income, and information shape choice.
- Sec 10.2Utility is the satisfaction a consumer receives from goods and services. Ordinal utility (ranking) is more realistic than cardinal utility (precise units). Total utility is the overall satisfaction from all units consumed.
- Sec 10.3Marginal utility is the additional satisfaction from one more unit, calculated as the change in total utility divided by the change in quantity. Marginal thinking focuses on incremental decisions, not all-or-nothing choices.
- Sec 10.4The law of diminishing marginal utility says each additional unit eventually adds less satisfaction than the last. It helps explain downward-sloping demand, diversified consumption, and why consumers stop where marginal benefit equals marginal cost.
- Sec 10.5A budget constraint shows all affordable combinations of goods given income and prices. Income changes shift the budget line in parallel; price changes rotate it, reflecting new relative prices.
- Sec 10.6The substitution effect shifts consumers toward relatively cheaper goods; the income effect reflects changed real purchasing power. Together they explain why demand curves slope downward, and why normal and inferior goods respond differently to income changes.
- Sec 10.7Consumer surplus is the gap between maximum willingness to pay and the price actually paid. It is the area between the demand curve and the price line, and it grows when prices fall.
- Sec 10.8Behavioral economics documents bounded rationality, framing effects, loss aversion, present bias, and status quo bias — patterns where real behavior departs from the standard rational-choice model without overturning its core predictions.
- Sec 10.9Consumer choice concepts explain everyday stopping decisions, household budgeting, responses to price changes, firm pricing strategies such as bundling and subscriptions, and the design of taxes, subsidies, and consumer protection policy.
Key Terms Review
utility
The satisfaction, benefit, or pleasure a consumer receives from consuming a good or service.
total utility
The overall satisfaction a consumer receives from all units of a good consumed.
marginal utility
The additional satisfaction a consumer receives from consuming one more unit of a good.
diminishing marginal utility (law of)
The principle that as a consumer consumes additional units of a good, the marginal utility of each additional unit eventually falls.
budget constraint
The set of all combinations of goods a consumer can afford given income and prices.
budget line
The graphical representation of the budget constraint, showing combinations of two goods that exactly exhaust income.
substitution effect
The change in quantity demanded resulting from a change in a good's price relative to the prices of substitutes.
income effect
The change in quantity demanded resulting from a change in real purchasing power caused by a price change.
normal good
A good for which demand increases as consumer income rises.
inferior good
A good for which demand decreases as consumer income rises.
consumer surplus
The difference between the maximum price a consumer is willing to pay and the price actually paid; the net benefit from a transaction.
behavioral economics
A field incorporating psychology into the study of economic decision-making, particularly where behavior departs from rational-choice predictions.
bounded rationality
The idea that human decision-making is constrained by limited information, cognitive capacity, and time.
framing effect
The influence of how a choice is presented on the decision made, independent of the underlying content of the choice.
loss aversion
The tendency to weight losses more heavily than equivalent gains.
present bias
The tendency to place excessive weight on immediate costs and benefits relative to those in the future.
Graph Review
Graph 10.1 — Total Utility and Marginal Utility
What to look for: Total utility rises as consumption increases, but at a decreasing rate. Marginal utility starts positive and falls. When marginal utility reaches zero, total utility is at its maximum (satiation). If marginal utility becomes negative, total utility falls.
Common Error
Students sometimes confuse total utility falling with marginal utility falling. Marginal utility falls throughout the pizza table in Section 10.3, but total utility still rises until the sixth slice. Total utility only falls when marginal utility turns negative.
Graph 10.2 — The Budget Line
What to look for: A straight line connecting the maximum quantity of Good A and the maximum quantity of Good B. Points on the line exactly spend income; points inside are affordable with money left over; points outside are unaffordable.
Slope interpretation: The slope equals the price ratio of the two goods (price of the horizontal-axis good ÷ price of the vertical-axis good).
Income change: Shifts the line in parallel; slope unchanged. Price change: Rotates the line around one intercept; slope changes.
Graph 10.3 — Consumer Surplus
What to look for: A downward-sloping demand curve and a horizontal market price line. Consumer surplus is the triangular area between the demand curve and the price line, to the left of the quantity purchased.
Shifts: A falling price grows the triangle; a rising price shrinks it. An outward shift in demand also grows consumer surplus at a given price.
Data Review
Working with a utility table: Build columns for quantity, total utility, and marginal utility. Calculate marginal utility as the change in total utility between adjacent rows. Verify marginal utility is declining and total utility peaks when marginal utility equals zero.
Working with a budget constraint: Given income and two prices, calculate the maximum quantity of each good affordable alone — these are the intercepts. Use the price ratio for the slope.
Calculating consumer surplus: With a linear demand curve and a given price, consumer surplus is a right triangle: Area = ½ × base × height, where base is quantity demanded and height is the gap between maximum willingness to pay and the market price.
Worked Example Review
Worked Example 10.1
Constructing a Marginal Utility Table
- SituationMarcus's total utility from cups of coffee: 0, 40, 72, 96, 112, 120, 120 for 0–6 cups.
- Step 1MU: 40, 32, 24, 16, 8, 0 for cups 1–6
- Step 2Confirm diminishing marginal utility: 40 → 32 → 24 → 16 → 8 → 0. ✓
- Step 3Identify satiation: at 6 cups, MU is zero and total utility peaks at 120. A seventh cup would add nothing or reduce utility.
Worked Example 10.2
Drawing a Budget Line
- SituationSofia has $60/week for fitness classes ($15) and books ($10).
- Step 1Vertical intercept: $60 ÷ $15 = 4 fitness classes
- Step 2Horizontal intercept: $60 ÷ $10 = 6 books
- Step 3Plot the line connecting (0, 6) and (4, 0).
- Step 4Slope = −(15 ÷ 10) = −1.5 — for every fitness class, Sofia gives up 1.5 books.
- Step 5If income rises to $90: new intercepts of 6 classes or 9 books; the line shifts outward in parallel; slope stays −1.5.
Worked Example 10.3
Calculating Consumer Surplus
- SituationConcert ticket demand has a vertical intercept of $120. The market price is $60, and 800 tickets are sold.
- CalculationCS = ½ × 800 × ($120 − $60) = ½ × 800 × $60 = $24,000
- ExtensionIf price falls to $40, quantity demanded rises and the consumer surplus triangle grows further.
Key takeaway: Consumer surplus calculations combine a price gap with a quantity to find a triangular area.
Concept Check
- What is the difference between total utility and marginal utility?
- State the law of diminishing marginal utility in your own words. Give an example from daily life not used in this chapter.
- What does a budget constraint show? What happens to the budget line when income increases?
- How does a price decrease in one good affect the budget line?
- Explain the substitution effect in plain language.
- Define consumer surplus. Why is it measured as the area between the demand curve and the price line?
- Name two findings from behavioral economics that challenge the standard model of perfectly rational consumers.
Practice Questions
Vocabulary in Context
- Rodrigo says, "I would have paid up to $80 for this jacket, but I bought it on sale for $50." What is Rodrigo's consumer surplus from this purchase?
- Classify each as relating primarily to total utility or marginal utility: (a) the satisfaction from eating your entire dinner; (b) how much better the fourth cookie tastes compared to the third; (c) the benefit from an entire month of gym membership.
- A consumer's income rises from $400 to $600 per month. What happens to her budget line? Does the slope change? Explain.
Graph Reasoning
- Draw a budget line for a consumer with $50 who can buy apples at $2 each or oranges at $2.50 each. Label both intercepts. What is the slope?
- Using the same budget line, show what happens if the price of apples falls to $1. Which intercept changes? What happens to the slope?
- Sketch a total utility curve and a marginal utility curve for a good with diminishing marginal utility. What does the total utility curve look like when marginal utility reaches zero?
Table Interpretation
Use the table below for question 14.
| Slices of Watermelon | Total Utility |
|---|
| 0 | 0 |
| 1 | 50 |
| 2 | 90 |
| 3 | 120 |
| 4 | 140 |
| 5 | 150 |
| 6 | 150 |
| 7 | 140 |
- (a) Calculate marginal utility for each slice. (b) At what quantity is total utility maximized? (c) At what quantity does the consumer experience negative marginal utility? (d) Does this table exhibit diminishing marginal utility? How do you know?
Consumer Surplus Problems
- A consumer is willing to pay at most $50 for a haircut. The salon charges $35. What is the consumer surplus?
- Suppose the market price of a textbook falls from $90 to $60. For a student who was already buying it at $90 and would have paid up to $120, how does consumer surplus change?
- If a market has a linear demand curve with a vertical intercept of $200 and a market price of $80, and 600 units are sold, calculate total consumer surplus.
Economic Reasoning Questions
- A student says, "I should keep eating because each additional slice of pizza still tastes good." A friend replies, "That doesn't mean you should keep eating — what matters is whether the extra slice is worth the cost." Who is applying marginal thinking more carefully? Explain.
- Why might a consumer who wins a coupon for a free good use the good even if she would not have bought it at any positive price? What does this tell you about consumer surplus at a price of zero?
- Explain in economic terms why people tend to diversify their consumption rather than spending all their money on one good.
- If the price of a bus ticket rises sharply, identify the substitution effect and the income effect for a daily commuter. In which direction do both effects push quantity demanded?
- Why might consumer surplus be larger in a competitive market than in a monopoly market? (Hint: think about the price level in each market structure.)
Policy Scenario Questions
- A city government proposes a tax on sugary beverages of $0.01 per ounce. Using consumer surplus and the substitution effect, explain the likely effects on consumers of sugary beverages.
- A housing authority sets a rent ceiling below the equilibrium market rent. Who benefits in terms of consumer surplus? What other effects might arise? Identify at least one unintended consequence.
- A government program provides low-income families with food vouchers. Compare the effect of this program on consumer choice to giving families the same dollar value in cash. Which gives consumers more flexibility? What are the arguments for each approach?
Error Analysis
- A student draws a budget line and shifts it outward when the price of one good falls, labeling the new line as parallel to the old one. Is the student correct? Explain what actually happens to the budget line when a price changes.
- A student constructs a marginal utility table and says, "Total utility is falling because marginal utility is falling." Identify the error.
- A textbook problem states that consumer surplus is the area below the price line and above the demand curve. Identify and correct the error.
- A student says that because the first slice of pizza has the highest marginal utility, the consumer should only eat one slice. What is wrong with this reasoning?
Real-World Applications
- You are comparing two grocery stores. Store A sells a bag of apples for $4; Store B sells the same bag for $3. You shop at Store B. Using consumer surplus, explain why you benefit from having both stores exist even though you only shop at one.
- A streaming service offers a bundle of movies, music, and audiobooks for $15/month, when the same services sold separately would cost $19. Many consumers buy the bundle. Use the concepts from this chapter to explain why.
- A student with a fixed monthly budget of $200 currently spends $100 on rent, $60 on food, and $40 on transportation. Rent increases to $130. Assuming income stays the same, what must happen elsewhere in the budget? Use the budget constraint to explain.
- Think of a purchase you have made recently. Estimate whether you had consumer surplus from that purchase. What was the most you would have paid? What did you pay?
- Loss aversion can explain why people are reluctant to sell items at prices other people consider fair. Describe a real-world example — from a garage sale, a used car market, or another context — and connect it to loss aversion.
Mixed Review
- A demand curve shifts rightward for a good. What happens to consumer surplus at the same market price? Draw a diagram to illustrate.
- (Review from Chapter 9) A good has very inelastic demand. When its price rises by 10%, quantity demanded falls by only 2%. Using what you now know about the substitution effect, why might inelastic demand be associated with few available substitutes?
- (Review from Chapter 6) How does the law of diminishing marginal utility help explain the negative slope of the demand curve? Connect the two ideas explicitly.
- (Review from Chapter 3) Is the money a consumer has already spent on a concert ticket a sunk cost when deciding whether to attend? How should a rational consumer think about this?
- Suppose a local government is considering whether to build a new public swimming pool, free to use. Using consumer surplus, explain how economists might estimate whether the pool creates net value for residents. What information would you need?
Common Misconceptions
Misconception 1
"Diminishing marginal utility means the consumer enjoys the good less and less."
Clarification: It means each additional unit adds less satisfaction than the previous one. The consumer may still enjoy every unit. Only when marginal utility turns negative does the consumer actively dislike consuming more.
Misconception 2
"Consumer surplus is a payment the consumer makes or receives."
Clarification: Consumer surplus is not a cash transfer. It is the value the consumer keeps — the gap between what she was willing to pay and what she actually paid.
Misconception 3
"A budget constraint only applies to poor people."
Clarification: Every consumer faces a budget constraint. Higher income expands it but does not eliminate it. Even a billionaire cannot afford everything.
Misconception 4
"Behavioral economics proves that people are irrational and economics doesn't apply to them."
Clarification: Behavioral economics refines and extends the standard model. Most core predictions of microeconomics still hold well; behavioral economics adds precision, not a complete rejection of economic reasoning.
Misconception 5
"The substitution effect and the income effect always reinforce each other."
Clarification: For normal goods, both effects push toward higher quantity demanded when price falls. For inferior goods, the income effect pushes the opposite way. In rare extreme cases (Giffen goods), the income effect can dominate. These are exceptional, not standard.
Looking Ahead
Chapter 11: Production, Costs, and Profit
Chapter 10 completed our study of the consumer side of markets. We now turn to the other side: producers and firms. Chapter 11 introduces production, costs, and profit — the foundation for understanding how firms make decisions. We will examine how firms convert inputs into outputs, how costs are structured, what distinguishes fixed from variable costs, and what profit means economically. These tools prepare us for Chapters 12 through 14, where we analyze different market structures and how competition shapes prices, output, and efficiency.
MGU Library Connection
- Economics Vocabulary Guide — Appendix K of this textbook
- Microeconomics Graph Reference — Appendix C of this textbook
- Formula and Calculation Reference — Appendix E of this textbook
- Consumer Surplus Guide — MGU Library Companion Resources
- Behavioral Economics Guide — MGU Library Companion Resources
- Chapter 9: Elasticity — develops the substitute-good reasoning used in Section 10.6
- Chapter 17: Information Problems and Behavioral Economics — develops Section 10.8 in full