Competition is not an attitude a company decides to have. It is a structure: how many sellers there are, how easily a new one can start, and whether buyers can walk away. Change the structure and the same people behave differently, which is why economists count sellers before they judge behavior. This room also opens a firm up — what a cost is, what profit actually measures, and why a business can be busy and still be losing. Five tabs — cards for the vocabulary, hints for the four structures, a quiz on structure and consequence, and a workshop where you sort markets, read a merger announcement line by line, order a market opening up and argue a real decision.
Many sellers, and a buyer who can walk to any of them. Nobody can hold the price up, because the next stall is three steps away.
Market power is not an attitude, a size or a mood. It is the number of doors the buyer has out of the room. Ask three questions in this order and you can predict the price without knowing anything about anyone's character: HOW MANY sellers are there, HOW HARD is it for a new one to start, and CAN THE BUYER go somewhere else. Everything in this unit — monopoly, oligopoly, barriers, antitrust — is one of those three answers.
What people get wrong
⚠️People often think…
A monopolist can charge whatever it wants.
Even the only seller faces a downward-sloping demand curve: push the price high enough and people do without, wait, repair the old one, or find a poor substitute. A monopolist chooses the point it likes best ON that curve — it never escapes the curve. That is why the interesting question is how much power it has, not whether it has any.
Constrained, not unlimited.
⚠️People often think…
A big company has market power and a small one does not.
Power is about the buyer's alternatives, not the seller's revenue. A national chain in a city with six rivals has less power over its customers than the only pharmacy in a county ten miles from the next one. Count the doors out of the room, not the size of the building.
Count alternatives, not revenue.
⚠️People often think…
A business with record revenue is doing well.
Revenue is everything coming in. Profit is what survives the costs. A bakery can sell twenty percent more bread, pay thirty percent more for flour and staff, and go quietly broke while every headline about it is good news. When someone tells you the revenue, the polite next question is what the costs were.
Revenue is a number. Profit is the answer.
⚠️People often think…
Competitors charging the same price must be colluding.
In a market with few sellers, prices moving together is exactly what competition looks like — each firm matches a rival's advertised price because it would lose customers otherwise. Collusion is the AGREEMENT, made privately, to hold a price up or split the customers. Identical prices are a reason to look; they are not the finding.
Matching is competing. Phoning first is a crime.
Worth knowing cold
The pairs worth knowing cold
Four pairs cover most of the mistakes in this unit. Learn each as two opposites, never as one blur.
Revenue / profitRevenue is price times quantity, everything coming in. Profit is revenue minus cost, what survives. A firm can set a revenue record and lose money.
Fixed / variable costFixed costs are paid whether you open or not — rent, license, insurance. Variable costs rise with output — flour, wages per shift. Only the variable part is in the decision to make one more.
Big / powerfulBig is revenue on a page. Powerful is how few alternatives the buyer has. The two often come apart, and questions are built on exactly that gap.
Competition / collusionMatching a rival's public price is competing. Agreeing privately to hold a price up, limit output or split the customers is collusion, and it is illegal.
Count, check entry, ask who can leave
1Watch one
Forty restaurants in one neighborhood, none quite like another, and a new one could open next year. Name the structure.
How many sellers? Forty. That rules out monopoly and oligopoly straight away.
Is the product identical? No — each one has its own menu, room and service.
How hard is entry? Not very. Restaurants open and close all the time.
Many sellers, differentiated product, easy entry: monopolistic competition. Each one has a little pricing power, and entry keeps it small. ✓
2Do one with me
Fill in the word or number each sentence is missing.
Revenue was $80,000 and total cost was $67,000. Profit was
Anything that makes it hard for a new firm to start competing is a barrier to
Competitors agreeing privately to hold a price up is called
💬One sentence, then you move on
Why do economists say a patent is a barrier to entry ON PURPOSE rather than a flaw in the law?
3Try one
A town has ONE pharmacy, ten miles from the next. A national chain has 3,000 stores in cities with six rivals each. Which one has more market power over its buyers?
I want a hint first
Count the doors out of the room for each set of buyers. One of these groups has six; the other has one, and it is ten miles away.
💬Last one — then you're done here
Where entry is easy, why do unusually high profits tend to disappear on their own?
Where this goes
Where this lives
Why there is one internet provider at your address, why the app everyone uses is hard to leave, why a drug costs a fortune for twenty years and almost nothing after, and why a town with one grocery store pays more for the same milk.
What this feeds
That is the whole 9–10 band. Next comes the other half of the subject: not one market, but the whole economy at once — what it produced, what it cost, and who had work.
Name one thing you buy where you have almost no alternative, and say what that does to its price.
One card at a time — tap “Show me” to check yourself, then Next. Start at Foundation; when those feel easy, climb.
Helpful Hints
🧭 The unit in one line
Count the sellers → ask how hard it is for a new one to start → ask whether a buyer has somewhere else to go → and you can predict the price without knowing a single thing about anyone's character.
How many, how hard to enter, and can the buyer leave.
🔑 The one idea
Market power is the ability to raise a price without losing all your buyers. It comes from structure — few sellers, hard entry, no substitute — and not from wanting it. That is why the remedy economists reach for is opening the market, not asking the firm to behave.
⚠️ Traps to avoid
A monopolist cannot charge any price it likes. It still faces a downward-sloping demand curve — raise the price far enough and buyers stop buying. It picks the point it likes best on that curve; it does not escape the curve.
Big is not the same as monopoly. A huge firm in a market with real rivals has less power than a small firm that is the only clinic in a county. Count the alternatives, not the revenue.
Profit is not revenue. Revenue is everything coming in; profit is what survives the costs. A business can take in more money every year and still be shrinking.
In economics, capital means tools and machines, not money. The oven is capital; the loan that bought it is not.
A patent is a barrier to entry ON PURPOSE. It trades some competition now for the incentive to invent at all. Calling it a flaw misses that it is the deal being struck.
Competing hard and colluding look similar from outside and are opposites. Matching a rival's public price is competition; agreeing in private to hold a price up is a crime.
📐 The four structures
Structure
Sellers
Entry
Example
Perfect competition
Very many, identical product
Free
Wheat, a commodity crop
Monopolistic competition
Many, differentiated product
Fairly easy
Restaurants, hair salons
Oligopoly
A few, watching each other
Hard
Airlines on a route, carriers
Monopoly
One, no close substitute
Blocked
The only water pipe into a town
Count the sellers, then check how hard it is to become one.
🎯 How you will be asked
“Which market structure is this, and what is your evidence?”
“Name two barriers to entry in this market.”
“Revenue was $80,000 and costs were $67,000. What was the profit?”
“Is this competition or collusion? How can you tell?”
“Why might a regulator allow one firm to be the only supplier of water?”
✅ Before the test, can you…
Put the four structures in order from fewest sellers to most?
Give three different kinds of barrier to entry?
Compute profit from revenue and cost, and say which is which?
Explain a natural monopoly without using the word “unfair”?
Say what antitrust law is actually aimed at?
🧠 Worth knowing cold
Revenue / profit — everything coming in, against what survives the costs.
Fixed / variable cost — the rent you pay whether you open or not, against the flour you buy per loaf.
Competition / collusion — matching a public price, against agreeing in private to hold one up.
Big / powerful — revenue on a page, against how many alternatives a buyer has.
Pick your level
Look back at anything you missed — the hint that appeared is exactly what to reread tonight.
How sure did you feel?
Workshop
Work like a competition regulator: sort twelve markets by their structure, read a merger announcement line by line, put the opening of a closed market in order, then make the call yourself.
Your practice never leaves this device. There is no account and no sign-in. Your work is saved in this browser only, and you can erase it whenever you want.
Your practice record — saved on this device
This is your record of the module on screen — it stays here and goes nowhere. Independent means you got it right on the first tap; supported means you got it after the explain-and-retry, or marked ‘I had it’ on a revealed answer. Both count, and neither is a grade. If your teacher asks, copy the row or show them this screen.
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