AP Macroeconomics Unit 1 ReviewBasic Economic Concepts

AP Macro Unit 1, Basic Economic Concepts, is the toolkit unit. It covers scarcity, opportunity cost, the production possibilities curve (PPC), comparative advantage, and supply and demand, which together explain how limited resources force choices and how markets settle on prices. The single biggest idea is scarcity. Because resources are limited and wants are not, every decision has an opportunity cost, and every model in this course is built on that fact. Unit 1 makes up 5-10% of the AP exam.

What this unit covers

Scarcity, trade-offs, and opportunity cost (Topics 1.1-1.2)

• Scarcity means society's wants exceed its resources. The factors of production (land, labor, capital, entrepreneurship) are limited, so using them one way means giving up another use. A few resources, like established knowledge, are non-rival and not scarce, but those are the exception.
• Opportunity cost is the value of the next best alternative you give up. It is the real cost of any choice, not just the dollar price. If you spend an hour studying macro, the opportunity cost is whatever you would have done with that hour instead.
• The production possibilities curve (PPC) draws this trade-off. With two goods on the axes, points on the curve are efficient (all resources fully used), points inside the curve are inefficient (resources sitting idle or misallocated), and points outside are unattainable with current resources and technology.
• The curve's shape tells you about opportunity costs. A bowed-out (concave) PPC means increasing opportunity costs, because resources are not equally good at producing both goods. A straight-line PPC means constant opportunity costs.
• The PPC shifts outward with economic growth (more resources, better technology, improved productivity) and inward with contraction (a disaster destroys capital, the labor force shrinks). Moving from inside the curve to a point on the curve is not growth; it is just using existing resources more fully.
• You also calculate opportunity cost from PPC data or tables. If producing 10 more computers means giving up 20 tons of wheat, the opportunity cost of one computer is 2 tons of wheat.

Comparative advantage and gains from trade (Topic 1.3)

• Absolute advantage means producing more of a good with the same resources. Comparative advantage means producing a good at a lower opportunity cost. These are different, and the exam loves to test that difference.
• Comparative advantage, not absolute advantage, determines who should specialize in what. Even a country that is worse at producing everything still has a comparative advantage in something.
• When producers specialize according to comparative advantage and then trade, both sides can consume combinations beyond their own PPC. That is the payoff of trade in one sentence.
• Terms of trade are the exchange rate between the two goods. For trade to benefit both sides, the terms must fall between each producer's opportunity costs. If wheat costs Country A 2 computers per ton and costs Country B 5 computers per ton, any trade price between 2 and 5 computers per ton makes both better off.
• Be ready to compute opportunity costs from an output table (who produces more per unit of resources) or an input table (who uses fewer resources per unit of output), then identify comparative advantage and a mutually beneficial trade.

Demand and supply (Topics 1.4-1.5)

• The law of demand says price and quantity demanded move in opposite directions, which gives the demand curve its downward slope. Higher price, fewer buyers willing and able to purchase.
• The law of supply says price and quantity supplied move in the same direction, which gives the supply curve its upward slope. Higher price, more production is worth it.
• A price change moves you along a curve. A change in a determinant shifts the whole curve. This distinction is the single most common Unit 1 error.
• Demand shifters include consumer income (normal vs. inferior goods), prices of substitutes and complements, tastes and preferences, expectations, and the number of buyers.
• Supply shifters include input prices, technology, taxes and subsidies, expectations, and the number of sellers. A rise in input prices shifts supply left; better technology shifts it right.

Market equilibrium and how prices adjust (Topic 1.6)

• Equilibrium is the price where quantity demanded equals quantity supplied. The market clears, with no leftover goods and no unsatisfied buyers at that price.
• A price above equilibrium creates a surplus (quantity supplied exceeds quantity demanded), and sellers cut prices to clear inventory. A price below equilibrium creates a shortage, and buyers bid prices up. Either way, market forces push price back toward equilibrium.
• You should be able to read the size of a surplus or shortage straight off a graph as the horizontal gap between the curves at a given price.
• When demand or supply shifts, equilibrium price and quantity change predictably. Demand right means price up and quantity up. Supply right means price down and quantity up. When both curves shift at once, one variable (price or quantity) is determinate and the other is indeterminate without knowing the sizes of the shifts.

Unit 1, Basic Economic Concepts at a glance

Why Unit 1, Basic Economic Concepts matters in AP Macro

Unit 1 is small on exam weight but enormous in leverage, because every later model is a Unit 1 idea scaled up. Aggregate demand and aggregate supply are supply and demand for the whole economy. Economic growth is the PPC shifting out. International trade is comparative advantage with countries as the players.

• Opportunity cost is the lens for every policy question in the course. Expansionary fiscal policy, holding money instead of bonds, and producing consumer goods instead of capital goods all have costs measured in foregone alternatives.
• The shift vs. movement-along distinction you learn here is exactly the logic you reuse with aggregate demand and aggregate supply, the money market, and the foreign exchange market.
• Equilibrium as the place markets settle, and disequilibrium as the force that moves prices, is the mental model behind output gaps and self-correction later in the course.

How this unit connects across the course

• The PPC shifting outward is your first picture of economic growth, which returns as long-run growth and the long-run aggregate supply curve shifting right (Unit 5). A point inside the PPC previews unemployment and recessionary output gaps (Unit 2).
• Supply and demand for a single market is the template for aggregate demand and aggregate supply, where the "price" is the price level and the "quantity" is real GDP (Unit 3).
• The equilibrium logic of Topic 1.6 reappears in the money market and the loanable funds market, where the price is an interest rate instead of a dollar price (Unit 4).
• Comparative advantage and terms of trade come back full force in the open economy, where they explain why countries trade and set up exchange rate and balance of payments analysis (Unit 6).

Key models and graphs to know

• Production possibilities curve (PPC): shows trade-offs, opportunity cost, efficiency, and growth for two goods. Bowed-out means increasing opportunity costs; straight means constant.
• Supply and demand graph: the workhorse model for finding equilibrium price and quantity and showing surpluses, shortages, and shifts.
• Opportunity cost calculation: opportunity cost of good X = amount of good Y given up / amount of good X gained. Use it for PPC questions and comparative advantage tables.
• Comparative advantage with two PPCs or a table: compare per-unit opportunity costs to assign specialization, then find terms of trade between the two opportunity costs.

Unit 1, Basic Economic Concepts on the AP exam

Unit 1 is 5-10% of the exam, the lowest weight of any unit, but its skills appear everywhere. Multiple-choice questions ask you to calculate opportunity cost from a PPC or a production table, identify which producer has comparative advantage and what terms of trade work, classify points on a PPC as efficient, inefficient, or unattainable, and predict the new equilibrium price and quantity after a demand or supply shift. Watch for double-shift questions where one outcome is indeterminate.

Free-response questions rarely focus only on Unit 1, but they constantly use it. You may need to draw a correctly labeled supply and demand graph, show a surplus or shortage at a given price, or explain a shift in words and on the graph. "Correctly labeled" is graded literally, so label the axes (price and quantity), the curves (S and D), and the equilibrium values. Graphing fluency built here pays off on every FRQ in the course.

Essential questions

• Why does scarcity force every individual, business, and government to make trade-offs?
• How does opportunity cost, rather than money price, measure the true cost of a decision?
• Why can two producers both gain from trade even when one is better at producing everything?
• How do prices coordinate the decisions of buyers and sellers without anyone in charge?

Key terms to know

• Scarcity: the condition of limited resources facing unlimited wants, forcing choices and trade-offs.
• Factors of production: the resources used to produce goods and services, namely land, labor, capital, and entrepreneurship.
• Opportunity cost: the value of the next best alternative given up when a choice is made.
• Production possibilities curve (PPC): a model showing the maximum combinations of two goods an economy can produce with its resources and technology.
• Increasing opportunity cost: the rising sacrifice of one good as more of the other is produced, shown by a bowed-out PPC.
• Absolute advantage: producing more of a good than another producer using the same quantity of resources.
• Comparative advantage: producing a good at a lower opportunity cost than another producer; the basis for specialization.
• Terms of trade: the rate at which goods exchange between trading partners, which must fall between the two producers' opportunity costs for both to gain.
• Law of demand: the inverse relationship between price and quantity demanded, producing a downward-sloping demand curve.
• Law of supply: the positive relationship between price and quantity supplied, producing an upward-sloping supply curve.
• Determinants of demand: non-price factors like income, related goods' prices, tastes, expectations, and number of buyers that shift the demand curve.
• Determinants of supply: non-price factors like input prices, technology, and number of sellers that shift the supply curve.
• Equilibrium: the price and quantity where quantity demanded equals quantity supplied and the market clears.
• Surplus and shortage: a surplus is excess quantity supplied at a price above equilibrium; a shortage is excess quantity demanded at a price below equilibrium.

Common mix-ups

• Absolute vs. comparative advantage: absolute advantage is about who produces more; comparative advantage is about who gives up less. Specialization and trade follow comparative advantage. A country can have absolute advantage in both goods but never comparative advantage in both.
• Change in demand vs. change in quantity demanded: a price change causes movement along the demand curve (change in quantity demanded). Only a change in a determinant, like income, shifts the curve itself (change in demand). Same logic for supply.
• Moving to the PPC vs. shifting the PPC: going from a point inside the curve to a point on it means using idle resources, not growth. Growth means the entire curve shifts outward.
• Surplus means price is too high, not too low: at a price above equilibrium, sellers offer more than buyers want, so price falls. Shortages happen below equilibrium and push price up.