Long-run Consequences and Open Economy — AP Macroeconomics Macro Study Guide

For: AP Macroeconomics candidates sitting AP Macroeconomics.

Covers: Long-run growth and productivity drivers, short and long-run Phillips curve dynamics, the crowding out effect, fiscal policy tradeoffs and government debt, and open economy exchange rate and net export relationships.

You should already know: No prior econ required.

A note on the practice questions: All worked questions in the "Practice Questions" section below are original problems written by us in the AP Macroeconomics style for educational use. They are not reproductions of past College Board papers and may differ in wording, numerical values, or context. Use them to practise the technique; cross-check with official College Board mark schemes for grading conventions.

1. What Is Long-run Consequences and Open Economy?

This unit bridges short-run macroeconomic fluctuation analysis and long-term economic performance, while introducing how national economies interact through international trade and financial markets. It constitutes 15-20% of the AP Macroeconomics multiple-choice section and is a frequent core topic for free-response questions (FRQs), often paired with aggregate supply-aggregate demand (AS-AD) model analysis. Common alternate labels for this content include long-run macro analysis and open-economy international macro.

2. Long-run growth and productivity

Long-run economic growth is defined as the sustained increase in an economy’s potential real GDP over time, measured most accurately by the annual percentage change in real per capita GDP (adjusted for inflation and population changes). The single largest driver of long-run growth is labor productivity, calculated as: $$\text{Labor Productivity}=\frac{\text{Real GDP}}{\text{Total Hours Worked}}$$ Four factors increase productivity: (1) physical capital stock (machinery, infrastructure, tools), (2) human capital (worker education, training, and health), (3) technological progress, and (4) accessible natural resources (a secondary driver for most advanced economies). The growth accounting formula breaks down GDP growth into its component inputs: $$\%\Delta \text{Real GDP}\approx \%\Delta \text{Labor}+\%\Delta \text{Capital}+\%\Delta \text{Total Factor Productivity (TFP)}$$ TFP (also called the Solow residual) captures unmeasured inputs like technological innovation and institutional efficiency.

Worked Example: An economy reports 1.8% growth in labor hours, 2.7% growth in capital stock, and 1.2% TFP growth. Its population grows at 1% per year. What is the growth rate of real per capita GDP? First, calculate total real GDP growth: $1.8+2.7+1.2=5.7\%$. Subtract population growth to get per capita growth: $5.7-1=4.7\%$. Exam tip: Examiners frequently test which policies drive long-run growth: R&D tax credits, public education funding, and infrastructure investment work, while short-term consumption stimulus does not shift long-run aggregate supply.

3. Phillips curve — short and long run

The Phillips curve models the relationship between inflation and unemployment, with distinct short-run and long-run dynamics. The Short-Run Phillips Curve (SRPC) is downward-sloping, reflecting a temporary tradeoff between inflation and unemployment when expected inflation and input prices are fixed. Its formula is: $$\pi ={\pi }^e-\alpha (u-u_n)$$ Where $\pi$ = actual inflation, ${\pi }^e$ = expected inflation, $\alpha$ = sensitivity of inflation to the unemployment gap, $u$ = actual unemployment, and $u_n$ = natural rate of unemployment (also called NAIRU, the non-accelerating inflation rate of unemployment). The Long-Run Phillips Curve (LRPC) is vertical at $u_n$, meaning no permanent tradeoff exists between inflation and unemployment. Over time, workers and firms adjust inflation expectations to match actual inflation, eliminating any short-run employment gains from higher inflation. SRPC shifters: changes in expected inflation, supply shocks (e.g., oil price hikes shift the SRPC up/right; positive tech shocks shift it down/left). LRPC shifters: changes in structural or frictional unemployment (e.g., higher minimum wage shifts LRPC right; improved job matching services shift it left).

Worked Example: Expected inflation is 3%, NAIRU is 4.5%, and $\alpha =0.8$. What is the inflation rate if actual unemployment is 7%? Plug in values: $\pi =3-0.8(7-4.5)=3-2=1\%$. If the central bank cuts interest rates to lower unemployment to 2%, inflation rises to $\pi =3-0.8(2-4.5)=3+2=5\%$.

4. Crowding out

Crowding out is the reduction in private investment spending that occurs when expansionary fiscal policy (higher government spending or tax cuts) increases real interest rates. The mechanism works as follows: expansionary fiscal policy increases the government budget deficit, so the government borrows more funds from the loanable funds market, raising demand for loanable funds and pushing up real interest rates. Higher interest rates raise borrowing costs for firms, reducing private investment spending. The magnitude of crowding out depends on the economy’s position:

• In a recession (output below potential), crowding out is minimal, as idle resources mean higher government spending does not compete heavily with private borrowers.
• At long-run full employment equilibrium, crowding out is nearly 100%: increased government spending fully replaces private investment, with no net change in real output, only higher price levels.

Worked Example: The government increases spending by $150B,financedbyborrowing.Realinterestratesrisefrom2$40B. If the marginal propensity to consume (MPC) is 0.75, what is the net short-run change in aggregate demand, assuming the economy is in a recession? First, calculate the spending multiplier: $\frac{1}{1-MPC}=\frac{1}{0.25}=4$. The government spending increase raises AD by $150\ast 4=600B$. The fall in private investment reduces AD by $40\ast 4=160B$. Net AD increase: $600-160=440B$.

5. Fiscal policy and government debt

Government fiscal balances are defined as a flow measure (annual): $$\text{Budget Balance}=\text{Tax Revenue (T)}-\text{Government Spending (G)}-\text{Transfer Payments (TR)}$$ A positive balance is a budget surplus, a negative balance is a budget deficit, and a zero balance is a balanced budget. National debt is the cumulative stock of all past budget deficits minus surpluses, the total amount the government owes to bondholders. The key metric for debt sustainability is the debt-to-GDP ratio: $$\text{Debt-to-GDP Ratio}=\frac{\text{Total National Debt}}{\text{Nominal GDP}}$$ If nominal GDP growth exceeds the annual deficit as a share of GDP, the debt-to-GDP ratio will fall over time, even with consistent deficits. Common debates about government debt include: (1) burden on future generations: debt held by foreigners reduces future domestic consumption as funds are sent abroad to repay bondholders, while domestically held debt is only a redistribution between taxpayers and domestic bondholders; (2) high debt levels can raise future borrowing costs and increase inflation risk if governments monetize debt.

Worked Example: A country has nominal GDP of $25T,nationaldebtof$17.5T, an annual deficit of 2% of GDP, and nominal GDP growth of 4% per year. What is its current debt-to-GDP ratio, and will it rise or fall over time? Current ratio: $\frac{17.5}{25}=70\%$. Since GDP growth (4%) is higher than the deficit as a share of GDP (2%), the ratio will fall over time.

6. Exchange rates and net exports

The nominal exchange rate ($e$) is the price of one currency in terms of another, e.g., $e=135$ JPY/USD means 1 US dollar buys 135 Japanese yen. The real exchange rate ($\epsilon$), which determines trade flows, adjusts for price level differences between countries: $$\epsilon =\frac{e\times P_{domestic}}{P_{foreign}}$$ Where $P_{domestic}$ = domestic price level, $P_{foreign}$ = foreign price level. A real appreciation (rise in $\epsilon$) makes domestic goods more expensive for foreigners and foreign goods cheaper for domestic residents, reducing exports and increasing imports, so net exports ($NX=Exports-Imports$) fall. A real depreciation (fall in $\epsilon$) increases net exports. Key exchange rate shifters:

• Higher domestic real interest rates attract foreign capital, increasing demand for domestic currency and causing appreciation.
• Higher domestic inflation makes domestic goods less competitive, increasing supply of domestic currency and causing depreciation.
• Higher domestic income increases demand for imports, increasing supply of domestic currency and causing depreciation.

Worked Example: If the European Central Bank raises interest rates relative to the US Federal Reserve, what happens to the EUR/USD exchange rate and US net exports to the EU? Euro-denominated assets become more attractive, so demand for euros rises and demand for dollars falls. The dollar depreciates relative to the euro (fewer euros per dollar). US goods become cheaper for EU consumers, so US exports to the EU rise, EU goods become more expensive for US consumers, so US imports from the EU fall, raising US net exports.

7. Common Pitfalls (and how to avoid them)

• Wrong move: Claiming a permanent tradeoff exists between inflation and unemployment. Why: Students only memorize the downward-sloping SRPC and forget the LRPC is vertical at NAIRU. Correct move: Always specify the time horizon: tradeoffs only exist in the short run when inflation expectations are fixed.
• Wrong move: Stating crowding out fully eliminates the effect of all expansionary fiscal policy. Why: Students learn the crowding out mechanism without context of the business cycle. Correct move: Crowding out is partial in recessions, and only full when the economy is at long-run full employment.
• Wrong move: Using budget deficit and national debt interchangeably. Why: Both refer to government spending shortfalls, so students mix up flow and stock measures. Correct move: Deficit is the annual amount the government overspends in one year; debt is the total accumulated amount owed from all past deficits.
• Wrong move: Assuming currency appreciation is always economically beneficial. Why: Students associate a "strong" currency with a strong economy. Correct move: Appreciation reduces net exports, lowering aggregate demand, which can worsen recessions.
• Wrong move: Attributing changes in expected inflation to a movement along the SRPC instead of a shift. Why: Students confuse demand shocks (movements along SRPC) and expectation/supply shocks (SRPC shifts). Correct move: Any change in expected inflation or input prices shifts the entire SRPC; demand shocks only cause movement along the existing curve.

8. Practice Questions (AP Macroeconomics Style)

Question 1 (Multiple Choice)

An economy is in long-run full employment equilibrium. The government passes a $250B stimulus bill financed by borrowing, with an MPC of 0.8. If full crowding out occurs in the long run, what is the net change in real GDP? A) +$1.25TB)+$250B C) $0D)-$500B

Solution: Correct answer is C. The spending multiplier is $\frac{1}{1-0.8}=5$, so the initial fiscal policy would raise AD by $250\ast 5=1.25T$ without crowding out. At full employment, higher government borrowing raises interest rates enough to reduce private investment by $250B,leadingtoa$1.25T fall in AD from crowding out. Net AD change is 0, so real GDP remains at potential, only the price level rises.

Question 2 (FRQ Part)

Country Y has a natural rate of unemployment of 5%, expected inflation of 2%, and SRPC given by $\pi ={\pi }^e-1.5(u-u_n)$. a) Calculate inflation if actual unemployment is 7%. b) If the central bank uses expansionary monetary policy to lower unemployment to 3% in the short run, what is the new inflation rate? c) Explain what happens to the SRPC and unemployment in the long run.

Solution: a) $\pi =2-1.5(7-5)=2-3=-1\%$ (1% deflation) b) $\pi =2-1.5(3-5)=2+3=5\%$ c) In the long run, workers and firms will adjust their inflation expectations upward to 5%, so the SRPC shifts up/right. Unemployment will return to the 5% natural rate, with permanent 5% inflation if policy remains unchanged.

Question 3 (FRQ Part)

Canada and Mexico are trading partners. Assume Canadian inflation rises significantly relative to Mexican inflation. a) What happens to the value of the Canadian dollar relative to the Mexican peso? Explain. b) What happens to Canadian net exports to Mexico? Explain.

Solution: a) The Canadian dollar depreciates relative to the peso. Higher Canadian inflation makes Canadian goods more expensive for Mexican consumers, reducing demand for Canadian dollars, and makes Mexican goods cheaper for Canadian consumers, increasing supply of Canadian dollars. The lower demand and higher supply of CAD pushes down the exchange rate (pesos per CAD falls). b) Canadian net exports to Mexico fall. Canadian goods are more expensive for Mexican buyers, so Canadian exports to Mexico fall, while Mexican goods are cheaper for Canadian buyers, so Canadian imports from Mexico rise. Since NX = exports - imports, NX decreases.

9. Quick Reference Cheatsheet

10. What's Next

This unit builds directly on foundational AS-AD, loanable funds, and aggregate demand concepts you learned earlier in the syllabus, and sets the stage for the final unit on international finance, where you will explore balance of payments accounts, trade deficit dynamics, and how monetary and fiscal policy operate under flexible and fixed exchange rate regimes. Long-run growth concepts are also frequently paired with production possibilities curve (PPC) analysis in FRQs, as long-run productivity growth shifts the PPC outward and the long-run aggregate supply curve to the right. To reinforce your mastery of these topics, work through official College Board past FRQs for Unit 5, paying close attention to mark scheme requirements for correctly labeling Phillips curve and foreign exchange market graphs. If you get stuck on any concept, practice problem, or past exam question, you can ask Ollie for step-by-step explanations, extra practice problems, or personalized review plans at any time by visiting the homepage.