Why is aggregate demand (AD) downward-sloping?

Question

BlackTom AI · Accepted Answer

Aggregate demand (AD) slopes downward primarily because a higher overall price level reduces real wealth and raises interest rates, both of which lower planned spending.

1. Relevant knowledge points and concepts
- AD is the total planned spending on goods and services at each price level (C + I + G + NX).
- Three standard channels make AD downward-sloping: the real-balances (wealth) effect, the interest-rate effect, and the exchange-rate (net-exports) effect. The answer choices capture the wealth effect and the general consequence that higher prices reduce willingness/ability to buy (which encapsulates the interest-rate and related effects).

2. Step-by-step reasoning
- Real-balances (wealth) effect: When the price level rises, the purchasing power of nominal money balances and nominal wealth falls. Consumers feel poorer and reduce consumption (C falls), so quantity demanded of output falls.
- Interest-rate effect: A higher price level increases demand for nominal money for transactions. With a fixed nominal money supply, money market equilibrium implies a higher nominal interest rate. Higher interest rates reduce investment (I) and some consumption, lowering AD.
- Exchange-rate effect (briefly): Higher domestic price level makes domestic goods relatively more expensive, reducing exports and increasing imports, so NX falls and AD falls.

3. Intermediate illustration (conceptual)
- Suppose nominal money balances are $1,000. If P increases 10%, real money balances = 1000 / 1.10 ≈ 909, a ~9.1% drop in purchasing power → lower C. Meanwhile money demand rises → interest rate ↑ → I falls.

4. Why the correct answer is correct
- The first option states the wealth effect (real purchasing power falls). The third option (“people are willing and able to buy less”) succinctly describes the net outcome including the interest-rate and other channels that reduce spending. Both mechanisms operate, so both statements are true and jointly explain the downward slope.

5. Why other options are incorrect
- Choosing only the first or only the third is incomplete because each captures only part of the story. “Neither of these” is incorrect because at least one and in fact both mechanisms are valid.

6. Conclusion
Both provided statements are correct explanations for why AD is downward-sloping; therefore the correct choice is “both of these,” which matches the given answer.

Why is aggregate demand (AD) downward-sloping?Single choice

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