AP Macroeconomics Unit 5 Review: Long-Run Consequences of Stabilization Policies

When the economy is in a recessionary gap, policymakers can use expansionary fiscal policy (increase G or cut taxes), expansionary monetary policy (increase money supply, lower interest rates), or both together to shift AD rightward toward full employment. In an inflationary gap, contractionary versions of each policy shift AD leftward. The policy mix matters: combining both tools can amplify effects on real output and the price level, but the two policies can also work at cross-purposes if one is expansionary while the other is contractionary.

• Recessionary gap response: Expansionary fiscal policy (raise G or cut T) and/or expansionary monetary policy (lower the federal funds rate via open-market purchases) both shift AD right, raising real output and the price level.
• Inflationary gap response: Contractionary fiscal policy (cut G or raise T) and/or contractionary monetary policy (raise interest rates via open-market sales) both shift AD left, reducing the price level and real output.
• Policy mix trade-offs: Expansionary fiscal policy paired with contractionary monetary policy can raise output while keeping inflation in check, but the net effect on interest rates and investment depends on the relative magnitudes.
• Interest rate channel: Monetary policy affects AD partly through interest rates: lower rates reduce the cost of borrowing, stimulating investment spending and consumer spending.

The Phillips curve translates the AD-AS model into inflation-unemployment space. The downward-sloping SRPC shows that in the short run, lower unemployment is associated with higher inflation. The vertical LRPC sits at the natural rate of unemployment, showing that no permanent trade-off exists. Long-run equilibrium is where the SRPC intersects the LRPC. Points left of that intersection represent inflationary gaps; points right represent recessionary gaps.

• SRPC movement (demand shocks): An increase in AD moves the economy up and left along the SRPC: unemployment falls and inflation rises. A decrease in AD moves the economy down and right: unemployment rises and inflation falls.
• SRPC shift (supply shocks): An adverse supply shock such as a sharp rise in oil prices shifts the SRPC upward: the economy experiences higher inflation and higher unemployment simultaneously, a condition called stagflation.
• LRPC and natural rate: The LRPC is vertical at the natural rate of unemployment. Factors that change the natural rate, such as changes in frictional or structural unemployment, shift the LRPC.
• Long-run equilibrium: The economy returns to the natural rate of unemployment in the long run as wages and prices adjust, placing it at the intersection of the SRPC and LRPC.
• Stagflation: A leftward shift of SRAS (or upward shift of SRPC) produces rising inflation and rising unemployment together, making standard demand-side policy responses ineffective on their own.

The quantity theory of money uses the equation MV = PY, where M is the money supply, V is the velocity of money, P is the price level, and Y is real output. When the economy is at full employment, V and Y are assumed stable in the long run, so sustained increases in M translate directly into proportional increases in P. Money is neutral in the long run: faster money growth raises inflation, not real GDP.

• MV = PY: The equation of exchange: money supply times velocity equals the price level times real output (nominal GDP). Rearranging, P = MV/Y.
• Monetary neutrality: At full employment in the long run, increasing M raises P proportionally but leaves Y unchanged, because real variables are determined by real factors, not the money supply.
• Short-run vs. long-run effects: In the short run, an increase in M can lower interest rates and raise AD, temporarily boosting real output. In the long run, only the price level rises.
• Calculating with MV = PY: If M = 500, V = 4, and Y = 1,000, then P = (500 x 4)/1,000 = 2. If M doubles to 1,000 and V and Y stay constant, P doubles to 4.
• Inflation as a monetary phenomenon: Sustained inflation over time results from the money supply growing faster than real output for an extended period, not from one-time price shocks.

A government budget deficit occurs when government purchases plus transfer payments exceed tax revenues in a given year. Each annual deficit adds to the accumulated national debt. Once debt exists, the government must pay interest on it, which itself becomes a spending obligation that can crowd out other priorities and compound the debt over time.

• Budget deficit formula: Deficit = Government purchases + Transfer payments - Tax revenues. A surplus is the reverse: revenues exceed expenditures.
• National debt accumulation: Each year's deficit is added to the national debt. A surplus reduces the debt. Running deficits year after year causes the debt to grow continuously.
• Interest payments on debt: The government must pay interest on outstanding debt. Higher debt means higher annual interest payments, which reduce the funds available for other government programs or tax cuts.
• Opportunity cost of debt service: Money spent on interest payments cannot be used for infrastructure, education, or other productive spending, creating a long-run fiscal constraint.

When the government runs a deficit, it borrows by issuing Treasury securities, which increases the demand for loanable funds. In the loanable funds market, this rightward shift in demand raises the equilibrium real interest rate. Higher real interest rates make borrowing more expensive for private firms and households, reducing interest-sensitive private investment spending. In the long run, less private investment means slower capital accumulation and lower economic growth.

• Crowding out definition: The decrease in private investment (and other interest-sensitive spending) caused by government borrowing that raises the real interest rate.
• Loanable funds market mechanism: Government deficit spending increases the demand for loanable funds, shifting the demand curve right, raising the equilibrium real interest rate, and reducing the quantity of private investment.
• Short-run effect: Higher real interest rates reduce business investment and consumer borrowing in the short run, partially offsetting the expansionary effect of the deficit spending.
• Long-run effect: Sustained crowding out reduces physical capital accumulation over time, lowering the economy's productive capacity and potential growth rate.

Economic growth is measured as the growth rate of real GDP per capita over time. The aggregate production function shows that output depends on the quantity of labor and capital and on the level of technology (total factor productivity). Labor productivity, measured as output per employed worker, rises when workers have more physical capital, more human capital, or access to better technology. An outward shift of the PPC is equivalent to a rightward shift of the LRAS curve.

• Real GDP per capita growth: Percent change in real GDP divided by population over a period; the standard measure of improvements in living standards over time.
• Aggregate production function: Shows that total output Y depends on labor L, physical capital K, and technology A. More capital or better technology raises output for a given amount of labor.
• Labor productivity: Output per employed worker. It rises with more physical capital per worker, more human capital per worker, or technological improvement.
• PPC and LRAS connection: An outward shift of the production possibilities curve reflects the same increase in productive capacity as a rightward shift of the LRAS curve: the economy can produce more at any price level.
• Diminishing returns to capital: Holding technology and labor constant, each additional unit of capital adds less to output than the previous unit, which limits growth from capital accumulation alone.

Public policies can raise long-run growth by increasing productivity or expanding labor force participation. Government investment in infrastructure and technology raises total factor productivity, shifting LRAS rightward. Supply-side fiscal policies, such as investment tax credits, R&D subsidies, and education funding, change incentives for households and businesses, affecting both aggregate supply and potential output. These policies differ from demand-side stabilization because their primary goal is expanding the economy's productive capacity.

• Supply-side fiscal policies: Tax and spending policies designed to increase productive capacity by improving incentives to work, save, invest, and innovate, shifting LRAS and SRAS rightward over time.
• Infrastructure investment: Government spending on transportation, broadband, and utilities lowers production costs for firms, raises TFP, and shifts LRAS rightward.
• Human capital policies: Education funding and job training raise worker productivity and labor force participation, increasing real GDP per capita over time.
• R&D and technology: Public investment in research and development or R&D tax credits encourages technological progress, the primary driver of sustained long-run growth.
• Labor force participation: Policies that bring more working-age people into the labor force, such as childcare subsidies or immigration reform, increase the labor input in the production function and raise potential output.