Course: ECO 2013, Principles of Macroeconomics | Textbook: Macroeconomics by Michael Parkin
Difficulty: Introductory | Prerequisites: None. This is the foundation for everything else in the course.
Module 1 builds the toolkit you will use for the rest of ECO 2013. It starts with the most basic economic problem (scarcity), introduces the core model of how markets work (demand and supply), then asks what happens when governments step into those markets, and finally extends the picture to international trade. If you skip this module or half-learn it, Modules 2 and 3 will feel much harder than they need to, because every later topic assumes you can read a supply-and-demand diagram and reason about trade-offs.
Economics begins with scarcity: we have unlimited wants but limited resources, so every choice has a cost. Markets coordinate buyers and sellers through demand and supply, and prices adjust until the quantity demanded equals the quantity supplied. Governments intervene with price controls, taxes, and trade restrictions, and each intervention creates predictable winners, losers, and efficiency effects.
Scarcity
The condition that arises because wants exceed the resources available to satisfy them. Every society, rich or poor, faces scarcity. Think of it as: you can't have everything, so you have to choose, and choosing means giving something up.
Opportunity cost
The highest-valued alternative forgone when you make a choice. It is not the dollar price; it is what you could have done instead. In simple terms, this means: the true cost of anything is the next-best thing you gave up to get it.
Production possibilities frontier (PPF)
A curve showing the maximum combinations of two goods an economy can produce when all resources are used efficiently. Points on the curve are efficient; points inside are inefficient; points outside are currently unattainable. Think of it as: the boundary of what is possible given your current resources and technology.
Marginal cost
The opportunity cost of producing one more unit of a good. Along the PPF, marginal cost typically increases as you produce more of a good, because resources are not equally suited to all tasks.
Marginal benefit
The benefit received from consuming one more unit of a good, measured by the maximum amount a person is willing to pay for it. Marginal benefit typically decreases as consumption increases.
Allocative efficiency
The point where marginal cost equals marginal benefit for each good. At this point, resources cannot be reallocated to make anyone better off without making someone else worse off.
Comparative advantage
The ability to produce a good at a lower opportunity cost than another producer. This is the basis for gains from trade, and it is different from absolute advantage. In simple terms: even if you are worse at everything than someone else, you can still gain from trade by specialising in whatever you are least bad at.
Absolute advantage
The ability to produce more of a good using the same quantity of resources, or the same amount using fewer resources. Having an absolute advantage does not determine who should specialise in what; comparative advantage does.
Demand
The relationship between the price of a good and the quantity demanded, holding all other influences constant (ceteris paribus). Represented by a downward-sloping curve.
Quantity demanded
The amount of a good consumers plan to buy at a specific price during a given time period. A change in price causes a movement along the demand curve, not a shift of it.
Supply
The relationship between the price of a good and the quantity supplied, holding other influences constant. Represented by an upward-sloping curve.
Quantity supplied
The amount of a good producers plan to sell at a specific price during a given time period.
Equilibrium price (market-clearing price)
The price at which quantity demanded equals quantity supplied. At this price, there is no tendency for the price to change.
Equilibrium quantity
The quantity bought and sold at the equilibrium price.
Surplus (excess supply)
When the price is above equilibrium, the quantity supplied exceeds the quantity demanded. Sellers compete, and the price falls.
Shortage (excess demand)
When the price is below equilibrium, the quantity demanded exceeds the quantity supplied. Buyers compete, and the price rises.
Change in demand vs. change in quantity demanded
A change in demand is a shift of the entire demand curve (caused by income, preferences, prices of related goods, expectations, or population). A change in quantity demanded is a movement along the curve caused by a change in the good's own price.
Change in supply vs. change in quantity supplied
A change in supply is a shift of the entire supply curve (caused by input prices, technology, expectations, number of sellers, or natural events). A change in quantity supplied is a movement along the curve caused by a change in the good's own price.
Normal good
A good for which demand increases when income increases.
Inferior good
A good for which demand decreases when income increases.
Substitute
A good that can be consumed in place of another. When the price of a substitute rises, demand for the original good increases.
Complement
A good that is consumed together with another. When the price of a complement rises, demand for the original good decreases.
Price ceiling
A government-imposed maximum price. If set below the equilibrium price, it creates a shortage. Rent controls are a common example.
Price floor
A government-imposed minimum price. If set above the equilibrium price, it creates a surplus. The minimum wage is a common example.
Tax incidence
The division of the burden of a tax between buyers and sellers. Tax incidence does not depend on who the tax is legally imposed on; it depends on the relative elasticities of demand and supply.
Deadweight loss
The reduction in total surplus (consumer surplus + producer surplus) that results from an inefficient level of production, such as that caused by a tax, price ceiling, or price floor.
Consumer surplus
The difference between the maximum price a buyer is willing to pay and the actual price paid, summed across all units purchased. Graphically, it is the area below the demand curve and above the price.
Producer surplus
The difference between the actual price received and the minimum price a seller is willing to accept, summed across all units sold. Graphically, it is the area above the supply curve and below the price.
Tariff
A tax on an imported good. It raises the domestic price, reduces imports, generates government revenue, but also creates deadweight loss.
Import quota
A quantitative limit on the amount of a good that can be imported. Like a tariff, it raises the domestic price and reduces imports, but the revenue equivalent (quota rent) goes to quota holders rather than the government.
Exports
Goods and services produced domestically and sold abroad. A country exports goods in which it has a comparative advantage.
Imports
Goods and services produced abroad and purchased domestically. A country imports goods in which other countries have a comparative advantage.
Every economic question traces back to scarcity. Because resources (land, labour, capital, entrepreneurship) are finite, producing more of one thing means producing less of another.
The PPF illustrates this trade-off. Its bowed-out shape reflects increasing opportunity cost: as you shift resources from one good to another, you lose more and more of the first good per unit of the second, because resources are not perfectly adaptable.
Economic growth shifts the PPF outward. This can result from more resources, better technology, or increased human capital. Growth does not eliminate scarcity; it just moves the boundary.
Allocative efficiency occurs where marginal benefit equals marginal cost. On the PPF, only one point is allocatively efficient for a given set of preferences.
Law of demand: other things equal, a higher price leads to a lower quantity demanded. This reflects both the substitution effect (buyers switch to alternatives) and the income effect (higher price reduces real purchasing power).
Demand shifters (things that shift the entire curve): income, prices of related goods, expected future prices, population/demographics, preferences.
Law of supply: other things equal, a higher price leads to a higher quantity supplied, because higher prices make production more profitable and cover higher marginal costs.
Supply shifters: input prices, technology, expected future prices, number of sellers, natural and institutional factors.
Market equilibrium is found where the demand curve intersects the supply curve. The model predicts that if the market is temporarily away from equilibrium, price adjustments will push it back.
To analyse a change, identify which curve shifts (or whether both shift), determine the direction of the shift, and then read off the new equilibrium price and quantity. Practise this process until it is automatic, because it comes up on every exam.
Price ceilings set below equilibrium cause shortages. Resources get wasted (queuing, searching), and the goods may not reach the people who value them most. Total surplus falls; deadweight loss appears.
Price floors set above equilibrium cause surpluses. Some willing buyers are priced out, and the surplus may require costly disposal or storage. Deadweight loss again.
Taxes drive a wedge between the price buyers pay and the price sellers receive. The quantity traded falls below the efficient level, creating deadweight loss. The size of the deadweight loss depends on the elasticities of demand and supply.
Tax incidence (who bears the burden) depends on relative elasticity. The more inelastic side of the market bears a larger share of the tax burden, regardless of whether the tax is legally levied on buyers or sellers. This is one of the most commonly tested points in the module.
Subsidies are negative taxes. They increase the quantity traded above the efficient level and also create deadweight loss, because units are being produced whose cost exceeds their value to consumers.
Gains from trade arise when countries specialise according to comparative advantage. Both countries can consume outside their individual PPFs.
The world price determines whether a country exports or imports a good. If the world price is above the domestic no-trade equilibrium price, the country exports; if below, it imports.
A tariff raises the domestic price above the world price, shrinks imports, increases domestic production, decreases domestic consumption, generates government revenue, and creates two triangles of deadweight loss.
An import quota has similar price and quantity effects to a tariff, but instead of government revenue, the gain goes to whoever holds the quota rights (quota rent).
Arguments for trade restrictions (infant industry, national security, dumping, environmental/labour standards) exist, but economists generally view most of these as less efficient than alternative policies. The course expects you to know the arguments and the standard critiques.
Opportunity cost on a linear PPF:
Opportunity cost of Good X = (units of Good Y given up) / (units of Good X gained)
If the PPF is a straight line from (0, 200 Y) to (100 X, 0), the opportunity cost of one X is 200/100 = 2 Y.
Consumer surplus = area of the triangle below the demand curve and above the market price.
Producer surplus = area of the triangle above the supply curve and below the market price.
Total surplus = consumer surplus + producer surplus. Maximised at the competitive equilibrium.
Deadweight loss from a tax = the triangle between the supply and demand curves, from the taxed quantity to the efficient quantity.
Rent control in cities like New York and San Francisco is a price ceiling. The predicted shortage shows up as long waiting lists, deteriorating housing quality, and black-market sublets.
The minimum wage is a price floor in the labour market. When set above the equilibrium wage, the model predicts a surplus of labour (unemployment), with the effect concentrated among low-skilled workers.
Tariffs on steel or aluminium raise domestic prices for downstream manufacturers (car makers, appliance producers), illustrating that trade policy creates both winners and losers within the same country.
Students often confuse a shift of the demand curve with a movement along it. A change in the good's own price causes a movement along the curve. Everything else shifts the curve. This distinction is tested relentlessly.
Students frequently think that whoever the tax is legally imposed on (buyer vs. seller) determines who really pays. It does not. Tax incidence depends on elasticities.
Many students treat absolute advantage and comparative advantage as the same thing. A country can have an absolute advantage in everything and still gain from trade by specialising where its opportunity cost is lowest.
Deadweight loss is not the same as a transfer. When a price ceiling redistributes surplus from producers to consumers, that redistribution is not deadweight loss. Deadweight loss is the surplus that simply disappears because trades that would have been mutually beneficial no longer happen.
⚠️ Shifting the correct curve (demand vs. supply) and in the correct direction is the single most important skill for Exam 1. Practise with novel scenarios until you can do it without hesitating.
⚠️ Tax incidence questions are a favourite. Remember: the more inelastic side bears the greater burden.
⚠️ You need to be able to draw and label a deadweight-loss triangle for taxes, price ceilings, and price floors.
⚠️ Know how to calculate opportunity cost from a PPF table or equation, and use it to determine who has the comparative advantage.
⚠️ The exam is multiple choice, closed-book, with a 3x5 handwritten notecard allowed. Prioritise formulas and diagrams on your notecard.
True or False: If the price of a good rises and quantity demanded falls, the demand curve has shifted to the left.
Fill in the blank: The opportunity cost of a choice is the _______ alternative forgone.
True or False: A price floor set below the equilibrium price will cause a surplus.
True or False: A country should only export goods in which it has an absolute advantage.
Fill in the blank: Deadweight loss from a tax is larger when demand and supply are more _______ (elastic/inelastic).
Answers:
False. This is a movement along the demand curve, not a shift.
Highest-valued.
False. A price floor below equilibrium has no effect; it must be above equilibrium to bind.
False. Trade is based on comparative advantage (lower opportunity cost), not absolute advantage.
Elastic.
Q: A freeze destroys a large portion of the Florida orange crop. Using the supply-and-demand model, what happens to the equilibrium price and quantity of oranges?
A: The supply curve shifts to the left (decrease in supply). At the original price, there is now a shortage, so the price rises. The new equilibrium has a higher price and a lower quantity.
Q: The government imposes a tax of $2 per unit on sellers of a good. Demand is perfectly inelastic. Who bears the burden of the tax?
A: Buyers bear the entire burden. When demand is perfectly inelastic (vertical demand curve), the full tax is passed on to buyers as a higher price. Sellers continue to receive the same net price.
Q: Country A can produce 10 cars or 50 tonnes of wheat. Country B can produce 8 cars or 20 tonnes of wheat. Which country has the comparative advantage in cars?
A: Country A's opportunity cost of 1 car = 50/10 = 5 tonnes of wheat. Country B's opportunity cost of 1 car = 20/8 = 2.5 tonnes of wheat. Country B has the comparative advantage in cars because its opportunity cost is lower.
Q: A binding price ceiling is imposed on a market. What happens to consumer surplus, producer surplus, and total surplus?
A: Producer surplus falls. Consumer surplus may rise or fall (some consumers gain from the lower price, but others lose because they cannot buy the good at all due to the shortage). Total surplus falls because deadweight loss is created.
Q: How does a tariff differ from an import quota in terms of who receives the revenue?
A: A tariff generates revenue for the government. An import quota generates quota rent, which goes to whoever holds the import licences. The price, production, and consumption effects are otherwise similar.
The demand-and-supply framework from this module reappears in Module 2 when you study the aggregate demand and aggregate supply model. The logic is the same, just applied to the entire economy rather than a single market.
Comparative advantage and trade connect directly to Module 3's coverage of exchange rates and the balance of payments. Understanding why countries trade sets up the question of how they pay for that trade.
Government intervention concepts (taxes, deadweight loss) feed into Module 3's fiscal policy material, where government spending and taxation are used as macroeconomic tools.
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