Lesson preview · Central Bank Tools
Central Bank Tools
~12 min · Free to read
The central bank wants borrowing to be cheaper. It announces a lower target for the short-term interest rate. But announcing is not the same as making it true. The bank cannot simply decree a rate and have the whole banking system obey. It has to act — pull levers that move the market until the actual rate lands where it wants. This lesson is the levers.
Start with the goal. The central bank targets a policy rate — a number it picks for the short-term interest rate banks charge each other. The last lesson showed where that rate comes from: it sits where the demand for money meets the supply of money, and the central bank controls the quantity of money. So to move the rate, the bank moves the money supply, or it changes how much banks want to lend. It has three main tools for that.
Before the tools, one word you need: reserves. Reserves are the money banks keep parked at the central bank — their cash on deposit there, available to lend out or to settle payments with other banks. More reserves in the system means banks have more to lend, which pushes interest rates down. Fewer reserves means less to lend, which pushes rates up. Keep that link in mind; every tool below works through it.
Key Term
Open market operations (OMO)
Open market operations (OMO) are the central bank buying or selling government bonds — and it is the main day-to-day tool.
- To ease (push the rate down), the bank buys government bonds. It pays for them with newly created reserves, so reserves flood into the banking system. The money supply rises, banks have more to lend, and the interest rate falls. This is expansionary policy.
- To tighten (push the rate up), the bank sells government bonds. Buyers pay with reserves, which drain out of the banking system. The money supply falls, banks have less to lend, and the interest rate rises. This is contractionary policy.
Think of the bank’s bond desk as a tap on reserves. Buying bonds opens the tap; selling bonds closes it.
Key Term
The reserve requirement
The reserve requirement is the fraction of deposits that a bank must keep as reserves rather than lend out. Say it is 10%: for every 100 in deposits, the bank holds 10 and may lend the other 90.
- Lowering the requirement frees banks to lend more of each deposit. More lending means more money circulating, so the interest rate falls. This eases policy.
- Raising the requirement forces banks to hold more and lend less of each deposit. Less lending means less money circulating, so the interest rate rises. This tightens policy.
The rate the bank charges does not change directly here. Instead the bank dials the volume of lending up or down.
Key Term
Interest on reserves (IOR)
Interest on reserves (IOR) is the rate the central bank pays banks on the reserves they park there. It is how big modern central banks — like the Federal Reserve — steer the rate today.
A bank always has a choice: lend its spare money out, or park it at the central bank and collect IOR. That choice depends on the IOR rate.
- Lowering IOR makes parking less rewarding, so banks lend instead. More lending pushes the market rate down. This eases policy.
- Raising IOR makes parking more attractive. Banks will not lend below what they can earn risk-free at the central bank, so the market rate gets pulled up with IOR. This tightens policy.
IOR acts like a floor under the market rate: move the floor and the rate moves with it.
Trap · Common Misconception
"The central bank just announces a rate and it happens"
It sounds like the central bank simply names a rate and the economy obeys. It does not. The bank publishes a target, but the actual rate is set in the market — by banks lending to each other. To make the target stick, the bank must act: buy or sell bonds to change reserves, adjust the reserve requirement, or move the interest it pays on reserves. The announcement only matters because everyone knows the bank will back it up with these tools. Interest on reserves is the closest thing to a directly-set rate — it works like a floor the bank can simply lift or lower — but even that is the bank acting, not just talking.
Tip
So what?
Every easing tool pushes the rate down by adding reserves or freeing up lending; every tightening tool pushes the rate up by draining reserves or restricting lending. Same logic, opposite directions.
Worked Example
The economy is overheating — spending and prices are climbing too fast — and the central bank wants to cool it down. It decides to tighten. Which way does it move each of its three main tools (open market operations, the reserve requirement, interest on reserves), and what happens to the interest rate in each case?
Check yourself · no marks
A central bank wants borrowing to be cheaper, so it carries out an open market purchase — it buys government bonds. Walk through why this pushes the interest rate down.
Commit to one first. Guessing and being wrong beats reading the answer cold.
Practice · 1 / 4
The central bank wants to ease policy and push the short-term interest rate down. Using open market operations, what should it do?
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