Fiscal Policy vs Monetary Policy

The difference that generates every other difference

One is political and one is technocratic, and almost everything else follows from that. Fiscal policy is the government spending money and collecting taxes, so it requires a law, which means committee hearings, a vote in both chambers, and a signature. Monetary policy is the Federal Reserve changing the money supply and interest rates, and the Federal Open Market Committee can decide that in an afternoon. This is why economists talk about fiscal policy having a long inside lag, the delay before anyone acts, while monetary policy has a short inside lag but a long outside lag, the delay before the action reaches the economy. If an exam question stresses that a response must be immediate, it is steering you toward the Fed. If it stresses that a specific group needs the money, it is steering you toward Congress, because the Fed cannot direct funds to a particular industry or household.

Direct versus indirect, on the graph

Expansionary fiscal policy shifts aggregate demand right immediately, because government purchases are literally one of the four components of AD alongside consumption, investment, and net exports. Expansionary monetary policy takes two steps. First the Fed buys bonds, the money supply rises, and the nominal interest rate falls in the money market. Only then does the lower interest rate encourage firms to borrow and invest and households to buy on credit, which is what shifts AD right. That is why a full-credit free-response answer on monetary policy usually needs two diagrams and a sentence connecting them, while a fiscal answer can often be made on one. Practice both on /sandbox/monetary-policy and /sandbox/fiscal-policy, and see the whole chain traced out at /graph-walkthroughs.

Crowding out is where the two collide

The interaction that examiners love is crowding out. When the government runs a deficit it borrows, which increases the demand for loanable funds, which raises the real interest rate, which discourages private investment. So expansionary fiscal policy partly undoes itself, and the AD shift is smaller than the initial spending suggests. Monetary policy has no equivalent problem, since the Fed increases the supply of money rather than competing for existing savings. In the long run this matters for growth: investment builds the capital stock, so persistent crowding out means a smaller future economy. Work the loanable funds diagram at /sandbox/loanable-funds until the chain from deficit to interest rate to investment is automatic, because it is the most commonly tested link between the two policies.

One detail almost every study site still gets wrong

Textbooks list three monetary tools: open market operations, the discount rate, and the reserve requirement. The reserve requirement is no longer among them in practice. The Federal Reserve Board reduced reserve requirement ratios to zero percent effective March 26, 2020, eliminating them for all depository institutions, and they have stayed there. The Fed's primary lever today is the interest rate it pays on reserve balances, which sets a floor under short-term rates. The AP course still expects you to reason about how a change in the required reserve ratio would affect the money multiplier, so learn the mechanism, but know that a question about what the Fed actually does now has a different answer than a question about what it could do in principle.

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