Monetary Policy Tools

The main tools central banks use to adjust the money supply and interest rates, from bond purchases to reserve requirements.

The Fed doesn’t control interest rates by simply announcing a new number and expecting the whole economy to obey. It has a specific toolkit for actually nudging money supply and interest rates in the direction it wants. Understanding these tools makes sense of a lot of financial news that otherwise sounds like technical noise.

Open market operations

The most frequently used tool is open market operations: the buying and selling of government bonds in financial markets. When the Fed buys bonds, it pays for them by effectively adding new money into the banking system, which increases the supply of money banks have available to lend, tending to push interest rates down. When the Fed sells bonds, it pulls money back out of the system, tending to push rates up.

Turning the tap on the money supply

Picture the banking system as a network of pipes carrying money between banks. When the Fed buys bonds from a bank, it's essentially opening the tap a little wider, sending more money flowing into that network - banks now have more to lend out, so the price of borrowing it (the interest rate) tends to drop. Selling bonds tightens the tap, pulling money back out and nudging rates back up.

This connects directly to the how-banks-create-money lesson: when banks receive more reserves through open market operations, they’re able to extend more loans, and each of those loans can, in turn, become new deposits elsewhere in the system.

The discount rate

The discount rate is the interest rate the Fed itself charges when banks borrow directly from it, often as a short-term backstop rather than a routine funding source, connecting to the lender-of-last-resort role covered in the previous lesson. Raising the discount rate makes this kind of direct borrowing more expensive, discouraging banks from relying on it; lowering it makes that option cheaper and more attractive. Because banks generally prefer borrowing from each other first, the discount rate acts more as a ceiling and a safety valve than as the everyday lever most rate changes run through.

Reserve requirements

A reserve requirement is the portion of deposits a bank is required to keep on hand rather than lend out, a concept introduced in the how-banks-create-money lesson. Raising reserve requirements forces banks to hold more money back, shrinking how much they can lend and tightening the money supply; lowering them frees up more money for lending. In practice, this tool has been used only sparingly in recent decades compared to open market operations, partly because even small changes to reserve requirements can have a large, fairly blunt effect across the entire banking system all at once.

Thinking all these tools are used equally often

It's easy to assume the Fed reaches for all its tools with similar frequency. In reality, open market operations are the daily workhorse, interest on reserves has become a key modern lever, the discount rate mostly sits in the background as a backstop, and reserve requirement changes are now rare. The tools exist together, but they aren't interchangeable in how often - or how bluntly - they get used.

Interest on reserves

A more modern tool involves the interest rate the Fed pays banks on the reserves they hold with it. By raising or lowering this rate, the Fed gives banks a direct incentive to either hold onto reserves rather than lend them out, or to lend more freely instead, giving policymakers a fairly precise, direct lever over short-term rates without needing to buy or sell large quantities of bonds.

How the tools work together

None of these tools operates entirely alone. The Fed typically sets a target range for the federal funds rate, covered in the previous lesson, and then relies mainly on open market operations and interest on reserves to keep the actual rate banks charge each other within that range, with the discount rate and reserve requirements serving as supporting instruments rather than primary levers. Together, these tools give the Fed a genuinely wide range of ways to expand or contract the money supply depending on what the economy needs at a given moment.

Key takeaways

Open market operations - buying and selling government bonds - is the Fed's most frequently used tool.
The discount rate is what the Fed charges banks that borrow directly from it, mostly as a backstop.
Reserve requirements set how much of each deposit a bank must hold back rather than lend out.
Interest on reserves gives banks a direct incentive to lend more or less freely.
These tools aren't used with equal frequency; open market operations and interest on reserves do most of the daily work.
Together, these tools let the Fed expand or contract the money supply to match economic conditions.