Microeconomics: Markets & Choice — Social Studies

What is scarce here — and why does that force a choice?

Opportunity cost is the value of the single next-best option you give up, not every option.

Explain why listing only a project's benefits gives an incomplete picture.

Alder faces a textbook problem of scarcity: it has 'one unused lakefront lot' and a grant that can fund only that lot, but three worthwhile wants competing for it. Because resources are limited while wants are not, the town cannot have everything and is forced to choose. That is what makes this an economic decision at all.

Choosing means accepting trade-offs — every option selected is other options refused. If Alder builds the conference center, it necessarily gives up both the playground and the wetland restoration on that lot. The opportunity cost, however, is specifically the value of the single next-best alternative it would otherwise have chosen — say the playground, if that was the runner-up. Opportunity cost is what you actually forgo by picking this option, so it is measured against the best sacrificed choice, not the sum of all rejected ones.

A good decision weighs that opportunity cost, not benefits alone, because every option has benefits. The conference center's projected visitor spending sounds attractive in isolation, but the real question is whether those gains are worth more than the best thing given up — the recreation a playground would provide, or the ecological and community value of a restored shoreline. Only by comparing an option's benefits against its opportunity cost can the council tell whether it is truly the best use of a scarce lot, rather than merely a use with some upside.

Response criteria

• Explains scarcity (limited lot and funds against unlimited wants) as the reason a choice is forced.
• Explains trade-offs — choosing one project means giving up the others.
• Correctly identifies the opportunity cost of the conference center as the value of the single next-best forgone option (the playground OR the wetland), not merely 'the other two.'
• Explains why weighing opportunity cost leads to a better decision than looking at benefits alone.

A frost affects the sellers' side — how much can be produced and offered for sale.

Did anything change about buyers' tastes or incomes? If not, demand held still.

Trace what happens to the equilibrium price and quantity when one curve moves.

This is a supply shock, not a demand change. The frost 'destroys about a third of the season's orange crop,' and oranges are the essential input for juice, so producers can make and offer far fewer cartons at every price. That is a decrease in supply — the supply curve shifts to the left.

Demand did not shift. The scenario is explicit that shoppers' 'tastes and incomes are the same as in December,' and nothing changed the price of substitutes or buyers' expectations. The amount people are willing to buy at each price is unchanged, so the demand curve stays put. What changed is only how much sellers can supply.

When supply shifts left while demand holds still, the market clears at a new equilibrium: a higher price and a lower quantity. With fewer cartons available, buyers bid the price up, and at that higher price the quantity actually purchased falls. That matches the scenario exactly — the price 'climbed noticeably' and 'the number of cartons sold has fallen.' So the frost raised prices and cut quantity by reducing supply, with demand unchanged.

Response criteria

• Correctly identifies that supply decreased (shifted left), not demand.
• Explains why supply fell (the frost destroyed a third of the oranges that juice production requires).
• Explains why demand did not shift (buyers' tastes and incomes were unchanged).
• Correctly connects the leftward supply shift to a higher equilibrium price and a lower quantity sold.

Beef and chicken are substitutes — what happens to a substitute's appeal when the other's price jumps?

Chicken's production costs did not change, so ask whether it is sellers or buyers who changed behavior.

A 'shift' is the whole curve moving because of an outside factor; a 'movement along' is caused only by that good's own price changing.

Beef and chicken are substitutes — goods buyers treat as alternatives for the same purpose, here the main dinner meat. When beef's price jumps from 5 to 8 dollars a pound, beef becomes a worse deal, so shoppers switch toward the alternative. Chicken looks relatively more attractive even though nothing about chicken itself changed, which is why 'shoppers are buying noticeably more chicken than before.'

This is an increase in the demand for chicken, not a change in chicken's supply. The scenario rules out a supply story: 'the cost of raising and processing chickens is exactly what it was,' so sellers did not become able or willing to offer more at each price. The change originated with buyers, whose willingness to buy chicken at every price rose because of an event in the beef market. That is a rightward shift of the chicken demand curve.

The distinction matters. A shift of the demand curve happens when an outside factor — here the price of a substitute — changes how much people want at every price; the whole curve moves. A movement along the demand curve happens only when the good's own price changes, causing buyers to slide to a different point on the same curve. Because chicken's own price did not fall — buyers are purchasing more at chicken's 'unchanged price' — this cannot be a movement along the curve. It must be a shift, driven by the higher price of the substitute, beef.

Response criteria

• Identifies beef and chicken as substitutes and explains that beef's higher price made chicken relatively more attractive.
• Correctly classifies this as an increase (rightward shift) in the demand for chicken, not a change in chicken's supply.
• Explains that chicken's supply and costs were unchanged, so the change came from the buyers' side.
• Correctly distinguishes a shift of the demand curve (caused by an outside factor like a substitute's price) from a movement along the curve (caused by the good's own price).

What can a Fairview customer do that a Gorham customer cannot when service is bad?

Think about how the threat of losing customers changes a company's incentives on price and quality.

The fix should restore some competitive pressure or a substitute for it (a rival, regulation, a public option).

Fairview and Gorham show what competition does and what its absence does. In Fairview, 'four companies offer service over the same streets,' so a customer who faces high prices or 'slow, unreliable connections' can switch to a rival. That threat of losing customers forces each company to keep prices down and quality up, which is why firms there 'boast about speed and price.' Competition pushes providers to compete on exactly the things customers care about, and it rewards innovation like faster equipment.

Gorham is a monopoly: 'a single company holds the only cable... with no competitor allowed.' Because customers have nowhere else to go, the company faces none of that pressure. It can charge 'about 40% more' for similar speeds, tolerate frequent outages, and skip upgrades 'in years' without losing the customers it would lose in a competitive market. Its behavior is a rational response to its incentives — with no rival to fear, spending on lower prices or better equipment would only cut its profit, so it does not.

That analysis points to the remedy: restore competition or a substitute for it. The mayor could allow a second provider onto the poles so residents gain the ability to switch, which would pressure the incumbent to cut prices and improve service the way Fairview's firms do. Alternatively, the town could regulate the monopoly's prices and reliability, or build a public broadband option. Each of these works by re-creating the discipline a monopolist otherwise escapes — the real possibility of losing customers.

Response criteria

• Explains how competition tends to lower prices and improve quality and innovation because customers can switch to rivals.
• Explains how a monopoly, facing no rival, can charge more and has weak incentives to improve (using Gorham's higher prices, outages, and lack of upgrades).
• Uses specific contrasts from the scenario (four providers vs. one; 40% higher prices; no upgrades).
• Suggests a plausible remedy (allow a competitor, regulate the monopoly, or create a public option) with reasoning.

At 900 dollars, how does the number of apartments people want to rent compare with the number landlords will offer?

Think about what a below-cost price does to landlords' incentive to build, maintain, and keep units as rentals.

Separate the winners (who got a cheap apartment) from the losers (who cannot find one, plus quality and black-market effects).

A rent cap is a price ceiling, and setting it at 900 dollars 'well below' the roughly 1,400-dollar market rent predictably creates a shortage. At the artificially low price, more people want apartments (quantity demanded rises) while landlords are willing to offer fewer (quantity supplied falls). When quantity demanded exceeds quantity supplied, the result is a shortage — exactly the 'long waiting lists' and vanished vacancies the scenario describes.

The other effects follow from landlords' incentives at the capped price. Because 900 dollars may not cover the return they could get otherwise, some 'converted apartments to condos for sale' and others 'stopped building new rental units,' shrinking supply further. Because the capped rent 'no longer covers upkeep,' some defer repairs, so quality falls. And because the legal price sits below what many renters would gladly pay, a gray market appears — apartments changing hands only to those who pay extra 'fees.' Each effect traces directly to a price held below the level that would balance the market.

The winners are the renters who already held apartments: they now pay less, 'as intended.' The losers are everyone shut out — newcomers who 'can barely find a vacancy,' current tenants facing deferred repairs, and future renters as building stalls. That gap between intention and result is the lesson: the council aimed at affordability but changed the incentives of the very people who supply housing. Good intentions did not guarantee a good outcome because prices are signals, and capping the signal without changing the underlying scarcity produced shortages, lower quality, and a black market instead of broad affordability.

Response criteria

• Explains that a price ceiling below the market price makes quantity demanded exceed quantity supplied, producing a shortage.
• Connects specific scenario effects (fewer units built, conversions to condos, deferred repairs, waiting lists, side 'fees') to the below-market cap and landlords' incentives.
• Analyzes winners (renters who kept units at the lower price) and losers (would-be renters who cannot find housing, plus quality and black-market effects).
• Explains why good intentions did not guarantee a good outcome (incentives and unintended consequences).

In each country, who decides what gets made — buyers and prices, or planners?

Think about what signal a market has (prices and profits) that a central plan lacks.

Every system has a strength: markets are responsive; central planning can pursue other goals like equality or stability.

Both countries answer the three basic economic questions, but through different mechanisms. In Country M's market system, what to produce is decided by buyers and prices: if a style 'sells out, firms rush to make more,' and 'unpopular styles are dropped.' How to produce and for whom are settled by profit and private ownership — the factors of production 'move toward whatever is most profitable,' and shoes go to those willing to pay. In Country C's command system, a 'central planning ministry decides each year how many shoes of each type to produce, sets the prices,' and assigns workers and materials in state-owned factories, so planners, not prices, answer all three questions.

That difference explains Country C's 'unwanted brown boots' piling up while shoppers 'wait months for the sneakers everyone actually wants.' A market continuously reads price and profit signals that reveal what people want and reallocates resources accordingly. Central planners have no such live signal: they must guess demand a year ahead, and 'when the plan guesses wrong,' there is no automatic mechanism to correct it, so surpluses and shortages persist. The missing information — the feedback that prices provide — is why the mismatch happens.

Still, each system has a genuine strength. The market's strength is responsiveness and efficiency: it adjusts quickly to what consumers want and rewards firms that satisfy them. The command system's strength is that central control can pursue goals a market ignores — directing resources toward shared priorities, guaranteeing everyone basic goods, or maintaining stability and full employment — even if it does so less efficiently. Neither is perfect; each trades away some of what the other does well.

Response criteria

• Explains that a market system answers what/how/for whom through prices, profits, and private ownership of the factors of production, while a command system answers them through central planning and state ownership.
• Uses specific scenario details (firms chasing profitable styles vs. the ministry setting output and prices).
• Analyzes why central planning produces the mismatch (planners lack the price signals that reveal what buyers actually want).
• Identifies at least one genuine strength of each system.

A poster changes attitudes; a charge changes the cost of an action. Which does economics predict works better?

Think about what the shopper now weighs at the register that they did not before.

Consider who a flat per-bag charge might burden, or how people might get around it.

Economics predicts this result because 'people respond to incentives.' A poster campaign only appeals to shoppers' good intentions, and intentions are easy to forget in a busy checkout line — which is why the neighboring city that 'tried posters alone saw almost no change.' A 10-cent charge does something different: it attaches a real, immediate cost to a specific action, so it changes the incentive rather than merely the message.

At the register, the charge reshapes the shopper's decision. Before, taking a disposable bag was free, so there was no reason to pause. Now each bag has a price, so the shopper weighs 10 cents against the small effort of bringing a reusable bag — and many decide the bag is not worth paying for. That is why the charge 'made customers pause at the register in a way the posters never did,' and why disposable-bag use 'dropped by roughly 60%' as people started 'keeping reusable bags in their cars.' A cost changed behavior that persuasion could not.

The council should still watch for downsides. A flat per-bag charge is somewhat regressive: 10 cents is trivial for a wealthy shopper but a real, if small, burden for a low-income family buying many bags, so the city might exempt certain benefit programs. It should also watch whether the effect fades once people stop noticing the charge, and whether shoppers simply shift to other single-use packaging. The incentive clearly works, but a well-designed policy monitors these side effects rather than assuming the charge is costless to everyone.

Response criteria

• Explains the principle that people respond to incentives, especially changes in cost or price, more reliably than to appeals alone.
• Analyzes how the 10-cent charge changes the shopper's decision by attaching a real cost to taking a disposable bag.
• Uses the scenario's evidence (posters produced almost no change; the charge cut bag use about 60%).
• Evaluates a plausible downside or limitation (e.g., burden on low-income shoppers, the small charge may stop working over time, shifting to other packaging).