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Scarcity and Opportunity Cost

Scarcity means unlimited wants versus limited resources, forcing every choice to have an opportunity cost.
  • Opportunity cost $=$ value of the next-best alternative given up
  • Every point on a Production Possibilities Curve (PPC) reflects a trade-off
  • 'There is no such thing as a free lunch' — even 'free' goods have opportunity costs
  • Sunk costs (already spent, unrecoverable) should NOT factor into future decisions
  • Explicit costs are direct payments; implicit costs are foregone alternatives (e.g., forgone wages)

Production Possibilities Curve (PPC)

The PPC shows the maximum combinations of two goods an economy can produce with fixed resources and technology.
  • Points on the curve $=$ full/efficient use of resources; points inside $=$ unemployment/inefficiency; points outside $=$ unattainable (currently)
  • Bowed-out (concave) PPC reflects increasing opportunity cost due to resources not being perfectly adaptable
  • A straight-line PPC implies constant opportunity cost (perfect resource substitutability)
  • Outward shift of the entire PPC $=$ economic growth (more resources, better technology, more capital)
  • A shift favoring one good only (e.g., a technology improvement in just one industry) rotates the PPC on that axis

Comparative Advantage & Specialization

Comparative advantage means producing a good at a lower opportunity cost than another producer, which is the basis for beneficial trade — even if one party has an absolute advantage in everything.
  • Absolute advantage $=$ producing more output with the same resources (compare total output)
  • Comparative advantage $=$ lower opportunity cost (compare trade-offs, not totals)
  • Mutually beneficial trade requires a terms-of-trade price between each party's own opportunity costs
  • Specialization based on comparative advantage increases total world output
  • A country can have absolute advantage in both goods but comparative advantage in only one

Demand

The Law of Demand states price and quantity demanded are inversely related, holding all else constant (ceteris paribus).
  • Determinants that shift demand: Tastes, Income (normal vs. inferior goods), Prices of related goods (substitutes/complements), Number of buyers, Expectations (memorize: T-I-P-N-E)
  • A change in price causes movement ALONG the demand curve (change in quantity demanded)
  • A change in a determinant shifts the ENTIRE demand curve (change in demand)
  • Normal goods: demand rises when income rises; inferior goods: demand falls when income rises
  • Substitutes: price of one rises, demand for the other rises; complements: price of one rises, demand for the other falls

Supply

The Law of Supply states price and quantity supplied are directly related, holding all else constant.
  • Determinants that shift supply: Resource (input) costs, Technology, Taxes/subsidies, Prices of other goods producers could make, Number of sellers, Expectations (memorize: R-O-T-T-E-N)
  • A change in price causes movement ALONG the supply curve (change in quantity supplied)
  • A change in a determinant shifts the ENTIRE supply curve (change in supply)
  • A per-unit tax on producers shifts supply left (up); a subsidy shifts supply right (down)
  • Improved technology or lower input costs shift supply to the right

Market Equilibrium & Price Controls

Equilibrium is where quantity demanded equals quantity supplied; government price controls that deviate from equilibrium create shortages or surpluses.
  • Price ceiling below equilibrium price causes a persistent shortage (e.g., rent control)
  • Price floor above equilibrium price causes a persistent surplus (e.g., minimum wage, agricultural price supports)
  • A price ceiling above equilibrium or a price floor below equilibrium is non-binding (no effect)
  • Simultaneous shifts: if both curves shift, one variable (price or quantity) is determinate and the other is ambiguous without more information
  • Consumer surplus $=$ area below demand, above price; producer surplus $=$ area above supply, below price
A price change moves you ALONG a curve, not the curve itself — only a determinant shifts the whole curve.
Absolute advantage is about who produces MORE; comparative advantage is about who gives up LESS — trade is based on the latter, not the former.
Sunk costs should be ignored in decision-making, not treated as a reason to 'stick with' a bad investment.
A country can have an absolute advantage in every good and still benefit from trade if comparative advantage differs.

Circular Flow Model

The circular flow model shows how money, goods, and resources move between households, firms, the government, and the foreign sector.
  • Households supply factors of production (land, labor, capital, entrepreneurship) to firms via factor markets
  • Firms supply goods and services to households via product markets, in exchange for spending
  • Leakages (savings, taxes, imports) remove money from the flow; injections (investment, government spending, exports) add money
  • For equilibrium GDP, leakages must equal injections: S + T + M $=$ I + G + X
  • The government and foreign sectors add complexity beyond the basic two-sector household-firm loop

GDP: Definition & Measurement

GDP (Gross Domestic Product) is the market value of all final goods and services produced within a country's borders in a given year.
  • Expenditure approach: GDP $=$ C + I + G + Xn (Consumption + Investment + Government spending + Net exports)
  • Only FINAL goods count — intermediate goods are excluded to avoid double-counting
  • Only production WITHIN the country's borders counts (GDP), regardless of who owns the resources (contrast with GNP, which is by nationality)
  • Investment (I) includes business investment in capital and inventories, and residential construction — NOT financial investments like stocks/bonds
  • Non-market and used-good transactions (housework, illegal sales, resale of used cars) are excluded from GDP

Nominal vs. Real GDP & the GDP Deflator

Nominal GDP measures output at current prices, while real GDP adjusts for inflation to allow comparison across years.
  • Real GDP $=$ (Nominal GDP / GDP Deflator) × 100
  • GDP Deflator $=$ (Nominal GDP / Real GDP) × 100, a price index for all goods in the economy
  • Real GDP uses constant base-year prices, isolating changes in actual output from changes in price level
  • If nominal GDP rises but real GDP falls, all the 'growth' was due to inflation, not more output
  • Real GDP per capita $=$ real GDP divided by population; used to measure living standards over time

Business Cycle

The business cycle describes the recurring pattern of expansion and contraction in real GDP over time.
  • Phases in order: expansion (growth) → peak → contraction/recession → trough → expansion again
  • A recession is commonly defined as two consecutive quarters of declining real GDP
  • Peak: economy at/near full employment and maximum output; Trough: output and employment at their lowest point
  • The long-run trend line represents potential/full-employment GDP; actual GDP fluctuates around it
  • A recessionary gap occurs when actual GDP < potential GDP; an inflationary gap occurs when actual GDP > potential GDP

Limitations of GDP

GDP is a useful but imperfect measure of a nation's economic well-being and total output.
  • Excludes non-market production: household labor, volunteer work, unpaid childcare
  • Excludes the underground/illegal economy (unreported cash transactions, black markets)
  • Does not measure quality of life, leisure time, income distribution, or environmental quality/externalities
  • Does not account for the composition of output (e.g., military goods vs. consumer goods) or negative externalities like pollution
  • GDP per capita can be misleading if income is highly unequally distributed across the population
GDP counts only FINAL goods, not intermediate goods — counting both would double-count the same value added.
'Investment' in macro means new capital goods and inventory changes, not buying stocks or bonds — don't confuse it with financial investing.
A rising nominal GDP does not necessarily mean the economy is actually producing more; check real GDP to rule out pure inflation.
GNP measures output by a country's citizens/firms anywhere in the world, while GDP measures output within a country's borders regardless of ownership — these are not interchangeable.

Measuring Unemployment

The unemployment rate measures the share of the labor force that is jobless and actively seeking work.
  • Unemployment rate $=$ (Number unemployed / Labor force) × 100
  • Labor force $=$ employed + unemployed (people who are actively seeking work); excludes discouraged workers and those not seeking work
  • Labor force participation rate $=$ (Labor force / Working-age population) × 100
  • Discouraged workers who stop looking for jobs are NOT counted as unemployed, which can understate true joblessness
  • Underemployed workers (part-time but wanting full-time work) are counted as fully employed, also understating labor market slack

Types of Unemployment

Economists classify unemployment by its underlying cause, which affects whether it signals a healthy or struggling economy.
  • Frictional: short-term, from workers transitioning between jobs or entering the labor force (natural and generally healthy)
  • Structural: mismatch between workers' skills/location and available jobs, often from technological change or industry decline
  • Cyclical: caused by a downturn in the business cycle (falls in a recession, rises in a boom); the only type tied to the business cycle
  • Seasonal: predictable, recurring unemployment tied to a time of year (e.g., agriculture, holiday retail)
  • Natural rate of unemployment (NRU) $=$ frictional + structural unemployment (assumes zero cyclical unemployment); economy is at full employment when actual $=$ natural rate

Inflation & the CPI

Inflation is a sustained rise in the general price level; the Consumer Price Index (CPI) is the most common tool to measure it.
  • CPI tracks the cost of a fixed 'market basket' of goods and services over time relative to a base year
  • Inflation rate $=$ [(CPI this year − CPI last year) / CPI last year] × 100
  • CPI can overstate inflation due to substitution bias, quality/new-product bias, and outlet bias
  • GDP deflator differs from CPI: the deflator covers ALL domestically produced goods (varies basket), CPI covers a FIXED basket of consumer goods (including imports)
  • Demand-pull inflation is caused by excess aggregate demand ('too much money chasing too few goods'); cost-push inflation is caused by rising input/production costs

Costs of Inflation & Redistributive Effects

Inflation redistributes wealth and imposes real economic costs, especially when unanticipated.
  • Menu costs: the real resource cost of updating prices
  • Shoe-leather costs: the cost/effort of holding less cash and making more trips to the bank to avoid inflation's erosion of money's value
  • Unanticipated inflation hurts lenders/creditors (repaid in less valuable dollars) and helps borrowers/debtors
  • Anticipated inflation is less costly because it can be built into contracts, wages, and interest rates (nominal rate $=$ real rate + expected inflation)
  • Inflation hurts people on fixed incomes (e.g., pensions) and savers holding cash; it helps those holding real assets or fixed-rate debt

Real vs. Nominal Values & the Fisher Equation

Nominal values are stated in current dollars; real values are adjusted for inflation to reflect true purchasing power.
  • Fisher equation: Nominal interest rate $=$ Real interest rate + Expected inflation rate
  • Real interest rate $=$ Nominal interest rate − Expected (or actual) inflation rate
  • Real income/wage growth $=$ Nominal income/wage growth − Inflation rate
  • If inflation exceeds the nominal interest rate, the real interest rate is negative — savers effectively lose purchasing power
  • Purchasing power of money moves inversely with the price level: as prices rise, each dollar buys less
'Full employment' means zero CYCLICAL unemployment, not zero unemployment overall — frictional and structural unemployment still exist.
Discouraged workers are NOT counted as unemployed because they've stopped searching, which can make the official unemployment rate understate true labor market weakness — this is a definitional trap, not a data error.
Inflation redistributes income; it does not automatically make everyone poorer — real asset holders and debtors can benefit from unanticipated inflation.
CPI inflation and GDP deflator inflation can differ because CPI uses a FIXED market basket including imports, while the deflator reflects all current domestic output.

Aggregate Demand (AD)

Aggregate demand is the total quantity of real GDP demanded by households, firms, government, and foreigners at each price level.
  • AD curve slopes downward due to three effects: wealth effect, interest rate effect, and foreign trade (exchange rate) effect
  • Wealth effect: higher price level reduces the real value of savings, so people spend less
  • Interest rate effect: higher price level raises interest rates (more money demanded), reducing investment/consumption
  • Foreign trade effect: higher domestic price level makes exports relatively more expensive and imports cheaper, reducing net exports
  • AD shifts (not movements) come from changes in C, I, G, or Xn — e.g., consumer confidence, tax cuts, interest rate changes, foreign income

Short-Run Aggregate Supply (SRAS)

SRAS shows the relationship between the price level and real GDP supplied in the short run, when input prices (especially wages) are sticky.
  • SRAS slopes upward because higher prices increase profits when input costs (wages) are fixed in the short run, encouraging more output
  • SRAS shifts left (decreases) with rising input/resource costs, negative supply shocks (e.g., oil price spike), or higher business taxes
  • SRAS shifts right (increases) with falling input costs, productivity improvements, or subsidies to producers
  • Stagflation $=$ SRAS shifts left, causing simultaneous higher price level (inflation) AND lower real GDP (recession/higher unemployment)
  • A supply shock is distinct from a demand shock: it moves price level and output in OPPOSITE directions

Long-Run Aggregate Supply (LRAS)

LRAS represents the economy's potential (full-employment) output, determined by resources, technology, and institutions — independent of the price level.
  • LRAS is a vertical line at potential/full-employment real GDP (natural rate of unemployment)
  • In the long run, wages and prices fully adjust, so changes in price level do not affect real output
  • LRAS shifts only from changes in the quantity/quality of resources, technology, or institutions — the same things that shift the PPC outward
  • The intersection of AD and LRAS represents long-run macroeconomic equilibrium
  • Economic growth is shown as a rightward shift of the LRAS curve (and PPC), not a movement along it

Short-Run Equilibrium & Output Gaps

Short-run macroeconomic equilibrium occurs where AD intersects SRAS; this may not coincide with full-employment output on LRAS.
  • Recessionary gap: SR equilibrium GDP < potential GDP (LRAS) — associated with high unemployment
  • Inflationary gap: SR equilibrium GDP > potential GDP (LRAS) — economy is 'overheating,' unsustainable in the long run
  • In a recessionary gap, high unemployment eventually pushes wages down, shifting SRAS right until it returns to LRAS (self-correction) — a slow process
  • In an inflationary gap, rising wages from labor shortages shift SRAS left, raising prices until output returns to LRAS
  • Policy is often used to speed up this adjustment rather than waiting for the slow, painful self-correction mechanism

Shifts, Multipliers & Combined Analysis

Changes in AD or AS shift the curves and change equilibrium price level and real GDP; the size of the AD shift depends on the spending multiplier.
  • An increase in AD shifts it right, raising both price level and real GDP (in the short run)
  • A decrease in AD shifts it left, lowering both price level and real GDP
  • Simultaneous AD and AS shifts: if AD rises and SRAS falls simultaneously, price level definitely rises but real GDP change is ambiguous
  • The multiplier effect: an initial change in spending leads to a larger shift in AD because one person's spending is another's income
  • Spending multiplier $=$ 1 / MPS $=$ 1 / (1 − MPC); this determines the horizontal size of an AD shift from a given change in spending
AD's downward slope is NOT the same reasoning as microeconomic demand (substitution among goods) — it comes from the wealth, interest rate, and foreign trade effects.
LRAS does not shift due to a change in price level — only changes in resources, technology, or institutions shift it (same as PPC shifts).
Stagflation (falling output + rising prices) comes from a leftward SRAS shift, NOT from an AD shift — AD shifts move price and output in the SAME direction, supply shocks move them in OPPOSITE directions.
'Full employment' equilibrium (AD $=$ LRAS $=$ SRAS) is a long-run concept; short-run equilibrium (AD $=$ SRAS) can sit above or below potential GDP.

Fiscal Policy Basics

Fiscal policy is the use of government spending and taxation, decided by Congress and the President, to influence aggregate demand and stabilize the economy.
  • Expansionary fiscal policy: increase government spending and/or decrease taxes to close a recessionary gap (shifts AD right)
  • Contractionary fiscal policy: decrease government spending and/or increase taxes to close an inflationary gap (shifts AD left)
  • Discretionary fiscal policy requires deliberate legislative action; automatic stabilizers work without new legislation
  • Automatic stabilizers: progressive income taxes and unemployment/welfare benefits that automatically counteract business cycle swings
  • Fiscal policy directly shifts AD; it does not directly affect the money supply (that's monetary policy)

The Spending Multiplier

Because one person's spending becomes another's income, an initial change in spending leads to a larger, magnified change in real GDP.
  • MPC (marginal propensity to consume) $=$ fraction of extra income spent; MPS (marginal propensity to save) $=$ fraction saved; MPC + MPS $=$ 1
  • Spending multiplier $=$ 1 / MPS $=$ 1 / (1 − MPC)
  • Total change in real GDP $=$ initial change in spending × spending multiplier
  • A higher MPC means a larger multiplier (more of each dollar gets re-spent, generating more rounds of income)
  • Government spending changes affect AD dollar-for-dollar times the multiplier; tax changes affect AD by less because part of a tax cut is saved, not spent

The Tax Multiplier

Tax changes affect AD indirectly through disposable income and consumption, making the tax multiplier smaller than the spending multiplier.
  • Tax multiplier $=$ −MPC / MPS $=$ −MPC / (1 − MPC)
  • The tax multiplier is smaller in absolute value than the spending multiplier because the first round of a tax cut is partly saved (only MPC × tax cut is spent)
  • A tax increase is contractionary (negative effect on GDP); a tax cut is expansionary (positive effect on GDP)
  • Balanced-budget multiplier: equal increases in G and T raise real GDP by exactly the amount of the spending increase (multiplier $=$ 1)
  • To calculate total effect: multiply the tax change by the tax multiplier, or the spending change by the spending multiplier, and sum for combined policies

Government Budget: Deficits, Surpluses & the National Debt

The budget balance is the difference between government revenue and spending in a given year; the national debt is the accumulation of past deficits.
  • Budget deficit: government spending > tax revenue in a given year (must borrow, issuing Treasury bonds)
  • Budget surplus: tax revenue > government spending in a given year
  • National debt $=$ the cumulative sum of all past deficits minus surpluses, accumulated over time
  • Expansionary fiscal policy (more spending/lower taxes) tends to increase deficits; contractionary fiscal policy tends to reduce them
  • Financing deficits by borrowing can lead to crowding out of private investment (see below)

Crowding Out & Supply-Side Fiscal Policy

Government borrowing to finance deficit spending can raise interest rates and reduce private investment, partially offsetting fiscal stimulus.
  • Crowding out: increased government borrowing raises interest rates (higher demand for loanable funds), which reduces private investment spending
  • Crowding out reduces the effectiveness of expansionary fiscal policy on real GDP
  • Supply-side fiscal policy (e.g., cutting tax rates, deregulation) aims to shift SRAS/LRAS right by increasing incentives to work, save, and invest
  • The Laffer Curve suggests tax revenue can rise OR fall with a tax rate cut depending on where the current rate sits relative to the revenue-maximizing rate
  • Supply-side policy differs from demand-side fiscal policy because it targets aggregate SUPPLY, not aggregate demand
A tax cut of $X does NOT shift AD by the same amount as a government spending increase of $X — the tax multiplier is smaller because part of the tax cut is saved, not all spent.
Automatic stabilizers (progressive taxes, unemployment benefits) work WITHOUT new legislation — don't confuse them with discretionary fiscal policy, which requires a new law.
Running a budget deficit in one year adds to, but is not the same as, the national debt — the debt is the cumulative stock, the deficit is the annual flow.
Fiscal policy shifts AD, not SRAS or LRAS directly — only supply-side fiscal policy (tax rate/incentive changes) is aimed at the supply side.

Functions & Definition of Money

Money is anything widely accepted as payment, and it serves three key economic functions.
  • Three functions of money: medium of exchange, unit of account, store of value
  • M1 $=$ currency in circulation + checkable (demand) deposits + traveler's checks — the most liquid measure of money
  • M2 $=$ M1 + savings deposits + small time deposits (e.g., CDs) + money market mutual funds — less liquid, broader measure
  • Money must be: durable, portable, divisible, and scarce (limited supply) to function well
  • Money is NOT wealth itself — it is a claim on wealth/goods, and its value depends on price level (purchasing power)

The Banking System & Fractional Reserve Banking

Commercial banks create money by lending out a fraction of their deposits, keeping the rest as required reserves.
  • Required reserve ratio (RRR) $=$ the fraction of deposits banks must hold, set by the Federal Reserve
  • Required reserves $=$ deposits × RRR; Excess reserves $=$ total reserves − required reserves
  • Banks can only loan out excess reserves — this is the basis of the money-creation process
  • A bank's simplified balance sheet: Assets (reserves, loans, securities) must equal Liabilities + Net Worth (deposits owed to customers)
  • When a bank makes a new loan, it creates new checkable deposits, i.e., new money, in the process

The Money Multiplier

Because each bank in the system re-lends its excess reserves, an initial deposit expands into a much larger increase in the total money supply.
  • Money multiplier $=$ 1 / RRR
  • Maximum change in the money supply $=$ initial change in excess reserves × money multiplier
  • The actual multiplier is often smaller than 1/RRR in reality due to cash leakage (holding currency) and banks holding excess reserves beyond the requirement
  • A higher RRR means a smaller money multiplier and less money creation from a given deposit
  • This multiplier process explains how the banking system, not just the Fed printing cash, expands the money supply

The Federal Reserve System

The Federal Reserve ('the Fed') is the U.S. central bank, responsible for conducting monetary policy and regulating the banking system.
  • The Fed's dual mandate: maximize employment and maintain stable prices (control inflation)
  • Structure: Board of Governors + 12 regional Federal Reserve Banks + the Federal Open Market Committee (FOMC), which sets monetary policy
  • The Fed is the 'lender of last resort' to commercial banks and regulates/supervises the banking system
  • The Fed does NOT control fiscal policy (spending/taxes) — that is Congress and the President's role
  • The Fed's balance sheet: Assets include government securities and loans to banks; Liabilities include currency in circulation and bank reserves

Money Market: Demand & Supply of Money

The money market determines the nominal interest rate through the interaction of money demand and the Fed-controlled money supply.
  • Money demand slopes downward: at lower interest rates, people hold more money (lower opportunity cost of holding cash) instead of interest-bearing assets
  • Money demand shifts with: changes in price level, real GDP/income, or expectations — NOT with interest rate changes (those cause movement along the curve)
  • Money supply is a vertical line, controlled by the Fed independent of interest rate
  • Equilibrium nominal interest rate is where money demand equals money supply
  • An increase in the money supply lowers the nominal interest rate (shifts supply right along a fixed demand curve); a decrease raises it
Banks can only lend out EXCESS reserves, not total reserves — required reserves must stay on hand.
The money multiplier (1/RRR) gives the theoretical MAXIMUM expansion of the money supply; actual expansion is usually smaller due to leakages and excess reserve holding.
The Fed controls the money supply and interest rates (monetary policy); it does NOT set government spending or tax rates (fiscal policy) — these are separate tools with separate policymakers.
A change in the interest rate causes a movement ALONG the money demand curve, not a shift of the whole curve — only price level, real income, or expectations shift money demand.

Tools of Monetary Policy

The Fed uses three main tools to change the money supply and influence interest rates.
  • Open market operations (OMO): the Fed's primary and most-used tool — buying government securities increases the money supply; selling decreases it
  • Reserve requirement: raising the RRR decreases the money supply (banks must hold more, lend less); lowering it increases the money supply
  • Discount rate: the rate the Fed charges banks for short-term loans; lowering it encourages more borrowing/lending, increasing the money supply
  • Federal funds rate: the rate banks charge EACH OTHER for overnight loans — the Fed targets this rate via OMO, it is not directly set by decree
  • Interest on reserves: paying banks interest on reserves held at the Fed can also influence how much banks choose to lend out

Expansionary & Contractionary Monetary Policy

Monetary policy targets the money supply and interest rates to influence investment, consumption, AD, and ultimately real GDP and price level.
  • Expansionary (easy money) policy: buy bonds / lower RRR / lower discount rate → increases money supply → lowers interest rates → used to close a recessionary gap
  • Contractionary (tight money) policy: sell bonds / raise RRR / raise discount rate → decreases money supply → raises interest rates → used to close an inflationary gap
  • Lower interest rates stimulate investment and interest-sensitive consumption (e.g., durable goods, housing), shifting AD right
  • Higher interest rates discourage investment and consumption, shifting AD left
  • Monetary policy operates with a transmission lag: money market changes → interest rate changes → investment/consumption changes → AD shift → real GDP/price level changes

Loanable Funds Market

The loanable funds market shows how the real interest rate is determined by the supply of savings and the demand for borrowing (investment).
  • Supply of loanable funds comes from savings (households, businesses, foreign lenders, government surplus)
  • Demand for loanable funds comes from borrowers (businesses investing, government financing deficits, consumers borrowing)
  • Equilibrium REAL interest rate is where supply of and demand for loanable funds intersect
  • An increase in government borrowing (deficit spending) shifts demand for loanable funds right, raising the real interest rate — this is the mechanism behind crowding out
  • An increase in private savings shifts the supply of loanable funds right, lowering the real interest rate

Money Market vs. Loanable Funds Market

The money market determines the NOMINAL interest rate in the short run via money supply/demand; the loanable funds market determines the REAL interest rate via saving/investment.
  • Money market: vertical money supply (set by Fed), downward-sloping money demand → determines nominal interest rate
  • Loanable funds market: upward-sloping supply of savings, downward-sloping demand for borrowing → determines real interest rate
  • Monetary policy (Fed action) is best modeled in the money market; fiscal policy/deficit effects are best modeled in the loanable funds market
  • Both markets are used together on the AP exam to trace: Fed action → money market rate change → loanable funds/investment change → AD shift → GDP/price level
  • Quantity of money (stock, e.g., \$ in the economy) is different from quantity of loanable funds (flow, e.g., \$ borrowed/lent per year)

Monetary Policy & the AD-AS Model (Full Chain)

Monetary policy's effects flow through several markets before reaching output and the price level — the AP exam frequently tests the full causal chain.
  • Expansionary chain: Fed buys bonds → money supply increases → nominal interest rate falls → investment/consumption rises → AD shifts right → real GDP rises, price level rises (closes recessionary gap)
  • Contractionary chain: Fed sells bonds → money supply decreases → nominal interest rate rises → investment/consumption falls → AD shifts left → real GDP falls, price level falls (closes inflationary gap)
  • The Phillips Curve shows a short-run trade-off between inflation and unemployment; in the long run it is vertical at the natural rate of unemployment
  • Easy money policy can worsen inflation if used when the economy is already at/above full employment
  • A liquidity trap or lag can weaken monetary policy's effectiveness even when the Fed acts correctly
The Federal funds rate is the rate banks charge each other, and the Fed only TARGETS it through OMO — it does not set it by direct decree like the discount rate.
Lowering the required reserve ratio INCREASES the money supply (banks can lend more) — a common sign-error trap.
Contractionary monetary policy raises interest rates and is used to fight inflation, not to fight a recession — don't reverse expansionary/contractionary with fiscal policy sign conventions.
The short-run Phillips Curve trade-off between inflation and unemployment disappears in the long run — the long-run Phillips Curve is vertical at the natural rate of unemployment.

Balance of Payments

The balance of payments records all economic transactions between a country's residents and the rest of the world.
  • Current account: records trade in goods/services (net exports), net investment income, and net transfers
  • Capital/financial account: records flows of financial assets — foreign investment, loans, purchases of securities and real estate
  • By definition, current account balance + financial account balance ≈ 0 (they must offset, since one records why money leaves/enters, the other how it does)
  • A current account deficit (importing more than exporting) is generally matched by a financial account surplus (net capital inflow financing that deficit)
  • Trade balance $=$ exports − imports; a trade deficit means imports > exports

Foreign Exchange (FOREX) Market

The foreign exchange market determines exchange rates through the supply and demand for currencies, driven by international trade and investment.
  • Demand for a currency comes from foreigners wanting to buy that country's exports or invest in its assets
  • Supply of a currency comes from that country's residents wanting to buy foreign goods or invest abroad
  • Currency appreciation: a currency becomes more valuable relative to another (buys more foreign currency)
  • Currency depreciation: a currency becomes less valuable relative to another (buys less foreign currency)
  • Exchange rates are determined by supply and demand for each currency in the FOREX market (flexible/floating exchange rate system)

Determinants of Exchange Rate Shifts

Several factors shift currency supply and demand curves, changing equilibrium exchange rates.
  • Relative interest rates: higher real interest rates in a country attract foreign investment, increasing demand for its currency, causing appreciation
  • Relative inflation rates: higher inflation makes a country's goods relatively more expensive, decreasing demand for its currency, causing depreciation
  • Relative income growth: rising domestic income increases demand for imports, increasing the supply of domestic currency, causing depreciation
  • Changes in preferences/expectations: if foreign goods or assets become more desirable, this shifts currency supply and demand accordingly
  • Central bank intervention: buying/selling currency reserves can also directly shift supply or demand in the short run

Effects of Exchange Rate Changes on Trade

Currency appreciation and depreciation directly affect a country's net exports and, through AD, its real GDP and price level.
  • Currency appreciation makes a country's exports MORE expensive to foreigners and imports CHEAPER for domestic residents → net exports fall
  • Currency depreciation makes a country's exports CHEAPER to foreigners and imports MORE expensive for domestic residents → net exports rise
  • A fall in net exports shifts AD left (contractionary effect); a rise in net exports shifts AD right (expansionary effect)
  • Appreciation of the domestic currency can help fight inflation (cheaper imports, less net export demand) but hurts export-dependent industries
  • These exchange-rate-driven AD shifts connect FOREX directly to the AD-AS model tested throughout the course

Linking Monetary Policy, Interest Rates & Exchange Rates

Domestic monetary policy affects interest rates, which in turn affects exchange rates and net exports — an important full-chain reasoning sequence on the AP exam.
  • Expansionary monetary policy → lower domestic interest rates → decreased foreign demand for domestic currency/increased demand for foreign assets → domestic currency depreciates
  • Currency depreciation → exports cheaper, imports pricier → net exports rise → AD shifts further right (reinforces expansionary policy)
  • Contractionary monetary policy → higher domestic interest rates → currency appreciates → net exports fall → AD shifts further left (reinforces contractionary policy)
  • This means exchange rate effects tend to REINFORCE, not offset, the direct effects of monetary policy on AD
  • Comparative advantage (Unit 1) is the underlying reason why countries engage in the trade being financed and exchanged here
Currency appreciation HURTS net exports (cheaper imports, pricier exports) — students often reverse this and think a 'stronger' currency helps exports.
A trade deficit is not inherently 'bad economics' — it is definitionally offset by a financial account surplus (capital inflows), not a sign of an accounting error.
Higher inflation relative to trading partners causes currency DEPRECIATION (less demand for now-less-competitive goods), not appreciation.
The exchange-rate effect of monetary policy reinforces the direct interest-rate effect on AD — it does not work in the opposite direction.
Term
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Unit 1: Basic Economic Concepts

Opportunity Cost
The value of the next-best alternative given up when a choice is made; the true cost of any decision.
Production Possibilities Curve (PPC)
A graph showing the maximum combinations of two goods an economy can produce with fixed resources and technology.
Absolute Advantage
The ability to produce more output of a good than another producer using the same amount of resources.
Comparative Advantage
The ability to produce a good at a lower opportunity cost than another producer; the true basis for beneficial trade.
Law of Demand
As the price of a good rises, quantity demanded falls, and vice versa, holding all else constant.
Law of Supply
As the price of a good rises, quantity supplied rises, and vice versa, holding all else constant.
Price Ceiling
A legal maximum price; if set below equilibrium, it is binding and causes a shortage.
Price Floor
A legal minimum price; if set above equilibrium, it is binding and causes a surplus.
Determinants of Demand
Non-price factors — income, tastes, prices of related goods, expectations, and number of buyers — that shift the entire demand curve.
Sunk Cost
A cost already incurred and unrecoverable; it should not influence rational future decisions.

Unit 2: Economic Indicators & GDP

Circular Flow Model
A diagram showing how money, goods, and resources flow between households, firms, government, and the foreign sector.
Gross Domestic Product (GDP)
The total market value of all final goods and services produced within a country's borders in a given period.
Expenditure Approach
A method of calculating GDP as C + I + G + Xn (consumption + investment + government spending + net exports).
Nominal GDP
GDP measured using current-year prices, not adjusted for inflation.
Real GDP
GDP adjusted for changes in the price level, allowing accurate comparison of output across years.
GDP Deflator
A price index measuring the average price level of all goods produced domestically, used to convert nominal GDP to real GDP.
Business Cycle
The recurring pattern of expansion, peak, contraction (recession), and trough in real GDP over time.
Recession
A significant decline in economic activity, commonly identified as two or more consecutive quarters of falling real GDP.
GNP (Gross National Product)
The total output produced by a country's citizens and firms, regardless of where in the world production occurs.
Limitations of GDP
GDP excludes non-market activity, leisure, income distribution, environmental costs, and the underground economy, limiting its use as a welfare measure.

Unit 3: Unemployment & Inflation

Unemployment Rate
The percentage of the labor force that is jobless, available for work, and actively seeking employment: (Unemployed / Labor Force) × 100.
Discouraged Worker
A person who wants a job but has stopped actively searching and is therefore excluded from the labor force and unemployment count.
Frictional Unemployment
Short-term unemployment from workers transitioning between jobs or entering the labor force for the first time.
Structural Unemployment
Unemployment caused by a mismatch between workers' skills and the skills employers demand, often due to technological change or industry decline.
Cyclical Unemployment
Unemployment caused by a downturn in the business cycle, rising during recessions and falling during expansions.
Natural Rate of Unemployment
The unemployment rate at full employment, consisting only of frictional and structural unemployment, with zero cyclical unemployment.
Consumer Price Index (CPI)
A price index measuring the cost of a fixed market basket of goods and services purchased by a typical urban consumer, used to track inflation.
Fisher Equation
The formula stating that the nominal interest rate equals the real interest rate plus the expected inflation rate.
Unanticipated Inflation
Inflation that is not expected, which redistributes wealth from lenders/savers to borrowers by eroding the real value of fixed nominal payments.
Stagflation
A combination of stagnant output (high unemployment) and high inflation occurring simultaneously, often caused by a negative supply shock.

Unit 4: AD-AS Model

Aggregate Demand (AD)
The total quantity of real GDP that all buyers in an economy are willing to purchase at each price level; slopes downward due to wealth, interest rate, and foreign trade effects.
Short-Run Aggregate Supply (SRAS)
An upward-sloping curve showing total output firms will produce at each price level in the short run, when input costs like wages are sticky.
Long-Run Aggregate Supply (LRAS)
A vertical curve at potential (full-employment) GDP, representing the economy's maximum sustainable output independent of the price level.
Recessionary Gap
A situation where short-run equilibrium real GDP is below potential GDP, associated with cyclical unemployment.
Inflationary Gap
A situation where short-run equilibrium real GDP exceeds potential GDP, associated with rising inflationary pressure.
Spending Multiplier
The factor by which an initial change in spending is multiplied to determine the total change in real GDP; equals 1/(1−MPC) = 1/MPS.
Marginal Propensity to Consume (MPC)
The fraction of an additional dollar of income that a household spends on consumption rather than saving.
Demand-Pull Inflation
Inflation caused by an increase in aggregate demand pulling the price level upward as the economy moves along SRAS.
Cost-Push Inflation (Stagflation)
Inflation caused by a leftward shift in SRAS due to rising production costs, which raises prices while lowering real output.
Self-Correction Mechanism
The long-run process by which wages and prices adjust to eliminate recessionary or inflationary gaps, moving the economy back to potential GDP without policy intervention.

Unit 5: Fiscal Policy

Fiscal Policy
The use of government spending and taxation, decided by Congress and the President, to influence aggregate demand and the overall economy.
Expansionary Fiscal Policy
Increased government spending and/or decreased taxes used to raise AD and close a recessionary gap.
Contractionary Fiscal Policy
Decreased government spending and/or increased taxes used to reduce AD and close an inflationary gap.
Tax Multiplier
The factor (−MPC/MPS) by which a change in taxes affects total GDP; smaller in absolute value than the spending multiplier because part of any tax change is saved.
Balanced-Budget Multiplier
The multiplier effect when government spending and taxes change by the same amount; always equal to 1.
Budget Deficit vs. National Debt
A deficit is the annual shortfall when spending exceeds revenue (a flow); the national debt is the cumulative total of past deficits minus surpluses (a stock).
Crowding Out
The reduction in private investment caused by government borrowing driving up interest rates in the loanable funds market.
Automatic Stabilizers
Government programs like progressive taxes and unemployment benefits that automatically counteract business cycle swings without new legislation.
Discretionary Fiscal Policy
Deliberate changes in government spending or taxation enacted through new legislation to influence the economy.
Supply-Side Fiscal Policy
Fiscal policy, such as tax incentives for investment, aimed at shifting aggregate supply rightward by improving production incentives.

Unit 6: Money, Banking & Fed

Money
Anything generally accepted as payment for goods/services and repayment of debt; must serve as medium of exchange, unit of account, and store of value.
M1 Money Supply
The most liquid measure of money: currency in circulation, checkable (demand) deposits, and traveler's checks.
M2 Money Supply
M1 plus near-monies: savings deposits, small time deposits (CDs under $100k), and retail money market mutual funds.
Required Reserve Ratio (rr)
The fraction of deposits banks must hold as reserves (not loan out), set by the Federal Reserve.
Excess Reserves
Reserves a bank holds beyond the required amount; these are the funds available for a bank to loan out.
Money Multiplier
1/rr — the maximum factor by which the money supply can expand from a new deposit of excess reserves through the banking system.
Federal Reserve (the Fed)
The central bank of the United States, responsible for regulating the money supply and implementing monetary policy.
T-Account (Bank Balance Sheet)
A simplified balance sheet showing a bank's assets (reserves, loans, securities) on the left and liabilities (deposits, net worth) on the right, used to track how a deposit changes the money supply.
Fractional Reserve Banking
A banking system in which banks keep only a fraction of deposits as reserves and lend out the rest, creating new money in the process.
Loanable Funds Market
The market where savers supply funds and borrowers (investors) demand funds; the real interest rate is the price that equilibrates saving and investment.

Unit 7: Monetary Policy

Tools of Monetary Policy
The Fed's three main tools: open market operations, the discount rate, and the required reserve ratio (also interest on reserves).
Open Market Operations
The Fed's buying (expansionary) or selling (contractionary) of government securities to change bank reserves and the money supply; the most frequently used tool.
Discount Rate
The interest rate the Fed charges commercial banks for short-term loans; lowering it is expansionary, raising it is contractionary.
Federal Funds Rate
The interest rate banks charge each other for overnight loans of reserves; the Fed targets this rate through open market operations.
Expansionary Monetary Policy
The Fed increases the money supply (buys bonds, lowers discount rate/rr) to lower interest rates, increase investment/consumption, and combat a recessionary gap.
Contractionary Monetary Policy
The Fed decreases the money supply (sells bonds, raises discount rate/rr) to raise interest rates, reduce spending, and combat inflation.
Money Market Model
Graph with interest rate on the vertical axis and quantity of money on the horizontal axis; money demand slopes downward, money supply is vertical (set by the Fed).
Quantity Theory of Money
MV = PQ, where M is money supply, V is velocity of money, P is price level, and Q is real output; in the long run, changes in M cause proportional changes in P (money neutrality).
Real vs. Nominal Interest Rate
Real interest rate = nominal interest rate − expected inflation; investment decisions depend on the real interest rate.
Money Neutrality
The long-run classical concept that changes in the money supply affect only nominal variables (price level) and not real variables (real GDP, employment).

Unit 8: International Trade & FOREX

Absolute Advantage
The ability of a producer to make a good using fewer resources/inputs than another producer.
Comparative Advantage
The ability of a producer to make a good at a lower opportunity cost than another producer; the basis for mutually beneficial trade.
Terms of Trade
The rate at which two countries agree to exchange goods; mutually beneficial terms lie between the two countries' opportunity cost ratios.
Balance of Payments
A record of all transactions between a country's residents and the rest of the world, composed of the current account and the capital/financial account.
Current Account
Records trade in goods and services (net exports), net income, and net transfers; a trade deficit means imports exceed exports.
Capital/Financial Account
Records international purchases of assets, such as foreign direct investment and portfolio investment; a surplus here offsets a current account deficit.
Foreign Exchange (FOREX) Market
The market where currencies are traded; the exchange rate is determined by the supply and demand for a currency.
Currency Appreciation
An increase in the value of one currency relative to another, making exports more expensive and imports cheaper.
Currency Depreciation
A decrease in the value of one currency relative to another, making exports cheaper and imports more expensive.
Determinants of Currency Demand/Supply
Relative interest rates, relative income/growth, relative price levels (inflation), and speculation/expectations shift currency supply and demand curves in the FOREX market.
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Unit 1: Basic Economic Concepts

Scarcity and Opportunity Cost
Scarcity means unlimited wants versus limited resources, forcing every choice to have an opportunity cost.
Production Possibilities Curve (PPC)
The PPC shows the maximum combinations of two goods an economy can produce with fixed resources and technology.
Comparative Advantage & Specialization
Comparative advantage means producing a good at a lower opportunity cost than another producer, which is the basis for beneficial trade — even if one party has an absolute advantage in everything.
Demand
The Law of Demand states price and quantity demanded are inversely related, holding all else constant (ceteris paribus).
Supply
The Law of Supply states price and quantity supplied are directly related, holding all else constant.
Market Equilibrium & Price Controls
Equilibrium is where quantity demanded equals quantity supplied; government price controls that deviate from equilibrium create shortages or surpluses.
Key fact
Opportunity cost is the value of the next-best foregone alternative — not just money spent.
Key fact
A bowed-out PPC shows increasing opportunity cost; a straight-line PPC shows constant opportunity cost.
Key fact
Comparative advantage (lowest opportunity cost) — not absolute advantage — determines mutually beneficial specialization and trade.
Key fact
Price ceilings below equilibrium cause shortages; price floors above equilibrium cause surpluses.

Unit 2: Economic Indicators & GDP

Circular Flow Model
The circular flow model shows how money, goods, and resources move between households, firms, the government, and the foreign sector.
GDP: Definition & Measurement
GDP (Gross Domestic Product) is the market value of all final goods and services produced within a country's borders in a given year.
Nominal vs. Real GDP & the GDP Deflator
Nominal GDP measures output at current prices, while real GDP adjusts for inflation to allow comparison across years.
Business Cycle
The business cycle describes the recurring pattern of expansion and contraction in real GDP over time.
Limitations of GDP
GDP is a useful but imperfect measure of a nation's economic well-being and total output.
Key fact
GDP $=$ C + I + G + Xn is the expenditure approach — memorize each component's exact meaning.
Key fact
Real GDP $=$ (Nominal GDP ÷ GDP Deflator) × 100 — always adjust nominal figures for price-level changes before comparing years.
Key fact
A recession is generally two consecutive quarters of falling real GDP; the trough is the low point, the peak is the high point.
Key fact
GDP excludes non-market activity, used goods, intermediate goods, and purely financial transactions.

Unit 3: Unemployment & Inflation

Measuring Unemployment
The unemployment rate measures the share of the labor force that is jobless and actively seeking work.
Types of Unemployment
Economists classify unemployment by its underlying cause, which affects whether it signals a healthy or struggling economy.
Inflation & the CPI
Inflation is a sustained rise in the general price level; the Consumer Price Index (CPI) is the most common tool to measure it.
Costs of Inflation & Redistributive Effects
Inflation redistributes wealth and imposes real economic costs, especially when unanticipated.
Real vs. Nominal Values & the Fisher Equation
Nominal values are stated in current dollars; real values are adjusted for inflation to reflect true purchasing power.
Key fact
Unemployment rate $=$ (Unemployed / Labor force) × 100; discouraged workers are excluded from the labor force entirely.
Key fact
Natural rate of unemployment $=$ frictional + structural unemployment; full employment does NOT mean zero unemployment.
Key fact
Fisher equation: nominal interest rate $=$ real interest rate + expected inflation.
Key fact
Unanticipated inflation redistributes wealth from lenders to borrowers; anticipated inflation has smaller real costs.

Unit 4: AD-AS Model

Aggregate Demand (AD)
Aggregate demand is the total quantity of real GDP demanded by households, firms, government, and foreigners at each price level.
Short-Run Aggregate Supply (SRAS)
SRAS shows the relationship between the price level and real GDP supplied in the short run, when input prices (especially wages) are sticky.
Long-Run Aggregate Supply (LRAS)
LRAS represents the economy's potential (full-employment) output, determined by resources, technology, and institutions — independent of the price level.
Short-Run Equilibrium & Output Gaps
Short-run macroeconomic equilibrium occurs where AD intersects SRAS; this may not coincide with full-employment output on LRAS.
Shifts, Multipliers & Combined Analysis
Changes in AD or AS shift the curves and change equilibrium price level and real GDP; the size of the AD shift depends on the spending multiplier.
Key fact
AD slopes down due to the wealth, interest rate, and foreign trade effects — not the Law of Demand's substitution logic.
Key fact
SRAS slopes up because of sticky input costs; LRAS is vertical at potential GDP, independent of price level.
Key fact
A recessionary gap is actual GDP < potential GDP; an inflationary gap is actual GDP > potential GDP.
Key fact
The spending multiplier $=$ 1/(1−MPC) $=$ 1/MPS determines how much an initial spending change shifts AD.

Unit 5: Fiscal Policy

Fiscal Policy Basics
Fiscal policy is the use of government spending and taxation, decided by Congress and the President, to influence aggregate demand and stabilize the economy.
The Spending Multiplier
Because one person's spending becomes another's income, an initial change in spending leads to a larger, magnified change in real GDP.
The Tax Multiplier
Tax changes affect AD indirectly through disposable income and consumption, making the tax multiplier smaller than the spending multiplier.
Government Budget: Deficits, Surpluses & the National Debt
The budget balance is the difference between government revenue and spending in a given year; the national debt is the accumulation of past deficits.
Crowding Out & Supply-Side Fiscal Policy
Government borrowing to finance deficit spending can raise interest rates and reduce private investment, partially offsetting fiscal stimulus.
Key fact
Spending multiplier $=$ 1/MPS $=$ 1/(1−MPC); Tax multiplier $=$ −MPC/MPS — the tax multiplier is always smaller in absolute value.
Key fact
Expansionary fiscal policy (↑G, ↓T) targets a recessionary gap; contractionary fiscal policy (↓G, ↑T) targets an inflationary gap.
Key fact
The balanced-budget multiplier (equal $ΔG$ and $ΔT$) equals 1 — GDP rises by exactly the amount of the spending increase.
Key fact
Government borrowing to finance deficits can crowd out private investment by raising interest rates.

Unit 6: Money, Banking & Fed

Functions & Definition of Money
Money is anything widely accepted as payment, and it serves three key economic functions.
The Banking System & Fractional Reserve Banking
Commercial banks create money by lending out a fraction of their deposits, keeping the rest as required reserves.
The Money Multiplier
Because each bank in the system re-lends its excess reserves, an initial deposit expands into a much larger increase in the total money supply.
The Federal Reserve System
The Federal Reserve ('the Fed') is the U.S. central bank, responsible for conducting monetary policy and regulating the banking system.
Money Market: Demand & Supply of Money
The money market determines the nominal interest rate through the interaction of money demand and the Fed-controlled money supply.
Key fact
Money multiplier $=$ 1/RRR; maximum money creation $=$ excess reserves × (1/RRR).
Key fact
M1 (most liquid: currency + checkable deposits) is a subset of the broader M2 (M1 + savings, small time deposits, money market funds).
Key fact
The Fed's dual mandate is maximum employment and price stability — it is achieved via monetary policy, not fiscal policy.
Key fact
Money demand slopes down against the interest rate (opportunity cost of holding money); money supply is vertical, set by the Fed.

Unit 7: Monetary Policy

Tools of Monetary Policy
The Fed uses three main tools to change the money supply and influence interest rates.
Expansionary & Contractionary Monetary Policy
Monetary policy targets the money supply and interest rates to influence investment, consumption, AD, and ultimately real GDP and price level.
Loanable Funds Market
The loanable funds market shows how the real interest rate is determined by the supply of savings and the demand for borrowing (investment).
Money Market vs. Loanable Funds Market
The money market determines the NOMINAL interest rate in the short run via money supply/demand; the loanable funds market determines the REAL interest rate via saving/investment.
Monetary Policy & the AD-AS Model (Full Chain)
Monetary policy's effects flow through several markets before reaching output and the price level — the AP exam frequently tests the full causal chain.
Key fact
Open market operations are the Fed's primary tool: buying bonds expands the money supply, selling contracts it.
Key fact
Expansionary monetary policy → lower interest rates → more investment → AD shifts right (used for recessionary gaps).
Key fact
The money market sets the nominal interest rate; the loanable funds market sets the real interest rate.
Key fact
Full causal chain: Fed action → money supply → interest rate → investment/consumption → AD → real GDP & price level.

Unit 8: International Trade & FOREX

Balance of Payments
The balance of payments records all economic transactions between a country's residents and the rest of the world.
Foreign Exchange (FOREX) Market
The foreign exchange market determines exchange rates through the supply and demand for currencies, driven by international trade and investment.
Determinants of Exchange Rate Shifts
Several factors shift currency supply and demand curves, changing equilibrium exchange rates.
Effects of Exchange Rate Changes on Trade
Currency appreciation and depreciation directly affect a country's net exports and, through AD, its real GDP and price level.
Linking Monetary Policy, Interest Rates & Exchange Rates
Domestic monetary policy affects interest rates, which in turn affects exchange rates and net exports — an important full-chain reasoning sequence on the AP exam.
Key fact
Currency appreciation makes exports more expensive and imports cheaper, reducing net exports and shifting AD left.
Key fact
Higher relative interest rates attract foreign investment, increasing demand for the currency and causing it to appreciate.
Key fact
Current account balance and financial account balance offset each other in the balance of payments.
Key fact
Expansionary monetary policy depreciates the currency, which reinforces (not offsets) the AD-increasing effect of lower interest rates.
Common mistakes for each unit — read the mistake, then make sure you know why it's wrong.

Unit 1: Basic Economic Concepts

Watch out
A price change moves you ALONG a curve, not the curve itself — only a determinant shifts the whole curve.
Watch out
Absolute advantage is about who produces MORE; comparative advantage is about who gives up LESS — trade is based on the latter, not the former.
Watch out
Sunk costs should be ignored in decision-making, not treated as a reason to 'stick with' a bad investment.
Watch out
A country can have an absolute advantage in every good and still benefit from trade if comparative advantage differs.

Unit 2: Economic Indicators & GDP

Watch out
GDP counts only FINAL goods, not intermediate goods — counting both would double-count the same value added.
Watch out
'Investment' in macro means new capital goods and inventory changes, not buying stocks or bonds — don't confuse it with financial investing.
Watch out
A rising nominal GDP does not necessarily mean the economy is actually producing more; check real GDP to rule out pure inflation.
Watch out
GNP measures output by a country's citizens/firms anywhere in the world, while GDP measures output within a country's borders regardless of ownership — these are not interchangeable.

Unit 3: Unemployment & Inflation

Watch out
'Full employment' means zero CYCLICAL unemployment, not zero unemployment overall — frictional and structural unemployment still exist.
Watch out
Discouraged workers are NOT counted as unemployed because they've stopped searching, which can make the official unemployment rate understate true labor market weakness — this is a definitional trap, not a data error.
Watch out
Inflation redistributes income; it does not automatically make everyone poorer — real asset holders and debtors can benefit from unanticipated inflation.
Watch out
CPI inflation and GDP deflator inflation can differ because CPI uses a FIXED market basket including imports, while the deflator reflects all current domestic output.

Unit 4: AD-AS Model

Watch out
AD's downward slope is NOT the same reasoning as microeconomic demand (substitution among goods) — it comes from the wealth, interest rate, and foreign trade effects.
Watch out
LRAS does not shift due to a change in price level — only changes in resources, technology, or institutions shift it (same as PPC shifts).
Watch out
Stagflation (falling output + rising prices) comes from a leftward SRAS shift, NOT from an AD shift — AD shifts move price and output in the SAME direction, supply shocks move them in OPPOSITE directions.
Watch out
'Full employment' equilibrium (AD $=$ LRAS $=$ SRAS) is a long-run concept; short-run equilibrium (AD $=$ SRAS) can sit above or below potential GDP.

Unit 5: Fiscal Policy

Watch out
A tax cut of $X does NOT shift AD by the same amount as a government spending increase of $X — the tax multiplier is smaller because part of the tax cut is saved, not all spent.
Watch out
Automatic stabilizers (progressive taxes, unemployment benefits) work WITHOUT new legislation — don't confuse them with discretionary fiscal policy, which requires a new law.
Watch out
Running a budget deficit in one year adds to, but is not the same as, the national debt — the debt is the cumulative stock, the deficit is the annual flow.
Watch out
Fiscal policy shifts AD, not SRAS or LRAS directly — only supply-side fiscal policy (tax rate/incentive changes) is aimed at the supply side.

Unit 6: Money, Banking & Fed

Watch out
Banks can only lend out EXCESS reserves, not total reserves — required reserves must stay on hand.
Watch out
The money multiplier (1/RRR) gives the theoretical MAXIMUM expansion of the money supply; actual expansion is usually smaller due to leakages and excess reserve holding.
Watch out
The Fed controls the money supply and interest rates (monetary policy); it does NOT set government spending or tax rates (fiscal policy) — these are separate tools with separate policymakers.
Watch out
A change in the interest rate causes a movement ALONG the money demand curve, not a shift of the whole curve — only price level, real income, or expectations shift money demand.

Unit 7: Monetary Policy

Watch out
The Federal funds rate is the rate banks charge each other, and the Fed only TARGETS it through OMO — it does not set it by direct decree like the discount rate.
Watch out
Lowering the required reserve ratio INCREASES the money supply (banks can lend more) — a common sign-error trap.
Watch out
Contractionary monetary policy raises interest rates and is used to fight inflation, not to fight a recession — don't reverse expansionary/contractionary with fiscal policy sign conventions.
Watch out
The short-run Phillips Curve trade-off between inflation and unemployment disappears in the long run — the long-run Phillips Curve is vertical at the natural rate of unemployment.

Unit 8: International Trade & FOREX

Watch out
Currency appreciation HURTS net exports (cheaper imports, pricier exports) — students often reverse this and think a 'stronger' currency helps exports.
Watch out
A trade deficit is not inherently 'bad economics' — it is definitionally offset by a financial account surplus (capital inflows), not a sign of an accounting error.
Watch out
Higher inflation relative to trading partners causes currency DEPRECIATION (less demand for now-less-competitive goods), not appreciation.
Watch out
The exchange-rate effect of monetary policy reinforces the direct interest-rate effect on AD — it does not work in the opposite direction.