2025 AP AP Macroeconomics 模擬試題連答案詳解

A.
- Draw an AD-AS graph with Price Level on the vertical axis and Real GDP on the horizontal axis.
- Plot downward-sloping \(\text{AD}\) and upward-sloping \(\text{SRAS}\) intersecting at \((\text{PL}_1, Y_1)\).
- Draw a vertical \(\text{LRAS}\) curve positioned to the left of \(Y_1\) at full-employment output \(Y_F\), illustrating an inflationary (positive) output gap.

B.
- (i) In an ample reserves framework, the central bank implements contractionary monetary policy by raising its administered rates (such as the Interest on Reserve Balances, IORB, or the discount rate / repo offering rate).
- (ii) In the reserve market graph (Policy Rate on vertical axis, Quantity of Reserves on horizontal axis):
* Draw a downward-sloping reserve demand curve that flattens into a horizontal floor at the administered rate (IORB), and a vertical reserve supply curve intersecting the flat portion.
* Shift the horizontal portion of the demand curve upward (raising the administered rate), showing a higher equilibrium policy rate.

C.
- Real output will decrease.
- Explanation: The higher policy rate transmits to higher commercial interest rates, which increases borrowing costs for households and firms. Consequently, interest-sensitive components of aggregate expenditure (consumer durables and business investment) decline, shifting aggregate demand leftward and reducing equilibrium real GDP.

D.
- (i) Financial capital will flow into Ardentia from Belmark because the relatively higher real interest rates in Ardentia offer global investors a higher rate of return on fixed-income financial assets.
- (ii) In the FOREX market for ARD (Exchange Rate \(\text{BMP}/\text{ARD}\) on vertical axis, Quantity of \(\text{ARD}\) on horizontal axis):
* The inflow of capital causes foreign investors to demand more ARD, shifting the demand curve \(D_{\text{ARD}}\) to the right (or Belmarkian investors supply fewer ARD, shifting \(S_{\text{ARD}}\) left).
* This results in an increase in the equilibrium exchange rate (appreciation of the Ardentian dollar relative to the Belmarkian peso).

E.
- Ardentia's net exports will decrease.
- Because the ARD appreciates, Ardentian goods become relatively more expensive to foreign buyers, reducing exports, while foreign goods become cheaper to domestic consumers, increasing imports.

Question 1 Scoring Guidelines (10 points total)

Part A (2 points):
- Point 1: Draw a correctly labeled AD-AS graph showing the short-run equilibrium at \(\text{PL}_1\) and \(Y_1\) at the intersection of aggregate demand (AD) and short-run aggregate supply (SRAS).
- Point 2: Include a vertical long-run aggregate supply (LRAS) curve positioned to the left of \(Y_1\) and labeled \(Y_F\).

Part B (3 points):
- Point 3: State that the central bank would increase its administered interest rates (or increase the interest rate on reserves / IORB rate).
- Point 4: Draw a correctly labeled graph of the reserve market with the vertical supply of reserves intersecting the demand for reserves in the flat/ample region.
- Point 5: Show an upward shift in the administered interest rate / lower bound of the reserve demand curve, resulting in an increase in the equilibrium policy rate.

Part C (1 point):
- Point 6: State that real output will decrease AND explain that higher interest rates reduce interest-sensitive spending (such as consumption or investment), causing aggregate demand to decrease.

Part D (3 points):
- Point 7: State that financial capital will flow into Ardentia (or capital inflows increase) AND explain that investors seek relatively higher returns/yields on Ardentian financial assets.
- Point 8: Draw a correctly labeled graph of the foreign exchange market for the Ardentian dollar (ARD) with axes labeled exchange rate (\(\text{BMP}/\text{ARD}\)) and quantity of ARD.
- Point 9: Show a rightward shift of the demand curve for ARD (or a leftward shift of the supply curve of ARD), leading to an increase in the equilibrium exchange rate (appreciation of the ARD).

Part E (1 point):
- Point 10: State that Ardentia's net exports will decrease.

A. In an ample-reserves framework, the primary tool of monetary policy is setting administered rates. To conduct expansionary monetary policy and close a recessionary gap, the central bank lowers the interest on reserve balances (IORB) rate (or administered rates).

B. On a correctly labeled graph of the reserve market:
- The vertical axis is labeled 'Policy Rate' (or 'Interest Rate') and the horizontal axis is labeled 'Quantity of Reserves'.
- The reserve demand curve has a downward-sloping portion and becomes horizontal at the administered rate floor (IORB).
- The vertical reserve supply curve intersects the demand curve in the horizontal (ample reserves) region.
- Decreasing the administered rate shifts the horizontal portion of the demand curve downward, lowering the equilibrium policy rate from \(PR_1\) to \(PR_2\).

C. As the policy rate decreases, nominal and real market interest rates fall, lowering the cost of borrowing for firms, which increases gross private domestic investment.

D. The aggregate price level will increase. The increase in gross private domestic investment increases aggregate expenditures, causing the aggregate demand (AD) curve to shift to the right along the upward-sloping short-run aggregate supply (SRAS) curve, driving up the equilibrium price level.

Part A (1 point):
- 1 point: States that the central bank would decrease the interest on reserve balances (IORB) or decrease administered interest rates.

Part B (2 points):
- 1 point: Draws a correctly labeled graph of the reserve market with the vertical supply curve intersecting the demand curve in the horizontal/flat range of ample reserves.
- 1 point: Shows a decrease in the administered interest rate (or downward shift of the horizontal segment of the demand curve for reserves), resulting in a decrease in the equilibrium policy rate.

Part C (1 point):
- 1 point: States that gross private domestic investment will increase.

Part D (1 point):
- 1 point: States that the price level will increase AND explains that the lower interest rate increases interest-sensitive spending (investment and/or consumption), which increases aggregate demand.

A. i. The graph should feature a vertical axis labeled 'Price Level' (or 'PL') and a horizontal axis labeled 'Real GDP' (or 'Real Output', 'Y'). The intersection of the downward-sloping Aggregate Demand (AD) curve and the upward-sloping Short-Run Aggregate Supply (SRAS) curve determines the equilibrium price level \(PL_1\) and real output \(Y_1\).
ii. Because the economy is operating below full employment (a recessionary gap), the vertical Long-Run Aggregate Supply (LRAS) curve must be placed to the right of \(Y_1\) and labeled \(Y_F\).

B. The government spending multiplier is:
\[ \text{Spending Multiplier} = \frac{1}{\text{MPS}} = \frac{1}{0.2} = 5 \]
To close a recessionary gap of $60 billion:
\[ \Delta G = \frac{\text{Output Gap}}{\text{Spending Multiplier}} = \frac{+\$60\text{ billion}}{5} = +\$12\text{ billion} \]
Thus, government spending must increase by $12 billion.

C. The marginal propensity to consume is \( \text{MPC} = 1 - \text{MPS} = 1 - 0.2 = 0.8 \).
The tax multiplier is:
\[ \text{Tax Multiplier} = -\frac{\text{MPC}}{\text{MPS}} = -\frac{0.8}{0.2} = -4 \]
To close the $60 billion gap:
\[ \Delta T = \frac{\text{Output Gap}}{\text{Tax Multiplier}} = \frac{+\$60\text{ billion}}{-4} = -\$15\text{ billion} \]
Thus, taxes must decrease by $15 billion.

D. Automatic stabilizers (such as progressive income taxes and unemployment benefits) respond automatically to economic downturns without new legislation. As output and income fall, tax receipts decrease automatically and transfer payments increase automatically. This prevents disposable income from falling by as much as output, thereby stabilizing consumer spending and reducing the contractionary effect on real GDP.

Point 1 (Part A.i): 1 point for drawing a correctly labeled AD-AS graph showing \(PL_1\) and \(Y_1\) at the intersection of the AD and SRAS curves.

Point 2 (Part A.ii): 1 point for showing a vertical LRAS curve to the right of \(Y_1\) and labeling the full-employment output as \(Y_F\).

Point 3 (Part B): 1 point for calculating the minimum change in government spending as an increase of $12 billion (or +$12 billion) and showing work:
\( \text{Spending Multiplier} = 1/0.2 = 5 \)
\( \Delta G = \$60\text{ billion} / 5 = \$12\text{ billion} \).

Point 4 (Part C): 1 point for calculating the minimum change in taxes as a decrease of $15 billion (or -$15 billion) and showing work:
\( \text{Tax Multiplier} = -0.8/0.2 = -4 \)
\( \Delta T = \$60\text{ billion} / (-4) = -\$15\text{ billion} \).

Point 5 (Part D): 1 point for explaining that as real output falls, automatic tax collections decrease and/or government transfers increase, which softens the decrease in disposable income and thereby supports consumption/aggregate demand.