Questions: Government Spending Multiplier in Macroeconomic Models

Question 1

An economy is operating normally with the central bank following a Taylor rule. The government increases spending by $100 billion. According to the New Keynesian model, what happens to aggregate output?

• A. Output rises by more than $100 billion as spending creates additional rounds of private consumption
• B. Output rises by exactly $100 billion because each dollar of spending becomes one dollar of output
• C. Output rises by less than $100 billion because the central bank raises interest rates in response to inflation, crowding out private spending
• D. Output is unchanged because private saving falls by exactly the amount of government spending

Answer: (C)

Under a Taylor rule, the central bank responds to fiscal-induced inflation by raising nominal interest rates more than one-for-one. This increase in interest rates raises the cost of borrowing and reduces private consumption and investment — the crowding-out effect. The net multiplier is therefore less than 1 (typically 0.5–1.0 in standard calibrations): a dollar of government spending generates less than a dollar of additional output because monetary tightening offsets part of the fiscal impulse. The simple Keynesian cross formula 1/(1-MPC) ignores this monetary feedback entirely.

Question 2

In a New Keynesian model, why is the government spending multiplier larger when the economy is at the zero lower bound (ZLB) than under normal conditions?

• A. At the ZLB the government borrows at zero interest rates, eliminating the fiscal cost of spending
• B. At the ZLB the central bank cannot raise nominal rates, so higher inflation expectations lower the real rate and amplify private spending
• C. At the ZLB households are financially distressed and spend a higher fraction of any income increase
• D. The multiplier is fixed at 2.0 at the ZLB by definition in New Keynesian models

Answer: (B)

At the ZLB, the nominal interest rate is stuck at zero, so the central bank cannot tighten in response to fiscal-induced inflation — the crowding-out channel is disabled. Instead, higher inflation expectations cause the real interest rate (nominal minus expected inflation) to fall, which stimulates private consumption and investment. The fiscal and private demand effects now reinforce rather than offset each other, creating a positive feedback loop. Under typical ZLB calibrations, multipliers can reach 1.5–2.0 or higher. This is the state-dependence: the same fiscal policy through the same model produces very different outcomes depending on the monetary regime.

Question 3

In the standard New Keynesian model with an active Taylor rule, the government spending multiplier is typically greater than 1.

• T. True
• F. False

Answer: False

This is the common misconception inherited from the simple Keynesian cross. The naive formula 1/(1-MPC) can produce large multipliers, but the New Keynesian model adds a crucial feedback: active monetary policy. When government spending raises output and inflation, the Taylor rule prescribes raising interest rates, which crowds out private spending. Standard calibrations produce multipliers between 0.5 and 1.0 under active monetary policy — less than one dollar of output per dollar of spending. Multipliers greater than 1 require either monetary accommodation (rates held fixed) or the ZLB.

Question 4

The government spending multiplier in New Keynesian models depends critically on the monetary policy regime, meaning two economists who agree on the model's structure can reach different conclusions about the size of the multiplier.

• T. True
• F. False

Answer: True

This is the central insight: the multiplier is not a fixed structural parameter but a policy-regime-dependent outcome. An economist assuming the central bank will fully accommodate the fiscal expansion (hold rates fixed) will estimate a large multiplier. An economist assuming an active Taylor rule will estimate a small multiplier. Both can be using the same model with the same MPC and the same parameter values — the disagreement is entirely about the assumed monetary policy response. This explains why economists who agree on theory can disagree sharply on policy: they are implicitly assuming different monetary regimes.

Question 5

Two economists both accept the New Keynesian model but disagree sharply about whether a large fiscal stimulus is a good idea. They are not disagreeing about the model's structure. What key assumption drives their disagreement about the multiplier's size?

Model answer: The key assumption is the monetary policy response. If the central bank follows an active Taylor rule, it raises interest rates in response to fiscal-induced inflation, partially offsetting the stimulus through crowding out (multiplier < 1). If the central bank is at the ZLB and cannot raise rates, higher inflation expectations actually lower the real rate and amplify the stimulus (multiplier > 1.5). Disagreement about what the central bank will do — or is constrained to do — produces the disagreement about fiscal effectiveness.

This is one of the most practically important insights in modern macroeconomics. The multiplier debate of the 2009–2010 stimulus period was largely a debate about monetary accommodation. Economists who thought the Fed would eventually tighten were skeptical of large multipliers; economists who thought the ZLB would persist for years predicted larger effects. Both camps used New Keynesian models. The empirical evidence broadly supports larger multipliers at the ZLB and during recessions, consistent with the theory.