Monetary Policy

A central bank controls one price directly: the rate at which banks lend reserves to each other overnight. Everything else follows through transmission channels. The interest rate channel moves the short end of the yield curve, and expectations about the future path of overnight rates pull longer maturities with them, altering the cost of capital for investment. The asset price channel works through discount rates: lower policy rates raise equity and property valuations, lifting household wealth and collateral values. The credit channel operates on bank balance sheets, since cheaper funding and stronger borrower collateral widen the supply of loans. The exchange rate channel matters most for open economies, where a lower relative rate tends to weaken the currency and support net exports.

Each channel carries a variable lag. The financial market response is immediate; the effect on output typically takes several quarters, and the effect on inflation longer still. This is why central banks act on forecasts rather than on realised data.

The policy rate is a target, not a decree. Central banks hit it by managing the supply of and demand for bank reserves. Open market operations buy or sell government securities, adding or draining reserves and pushing the interbank rate toward target. Most modern frameworks use a corridor: a lending facility rate above target caps the market rate, because no bank pays more than it can borrow at from the central bank, while a deposit facility rate below target sets a floor, because no bank lends below what it earns risk-free on reserves. Reserve requirements remain a tool in some jurisdictions but are rarely used for fine-tuning in developed markets.

When the policy rate reaches its effective lower bound, the balance sheet becomes the instrument. Quantitative easing purchases longer-dated assets to compress term and risk premia, while forward guidance commits to a future rate path in order to influence expectations today. Quantitative tightening reverses the process, allowing holdings to roll off or selling them outright.

Whether policy is expansionary or contractionary cannot be read from the level of the policy rate alone. The reference point is the neutral rate, the real rate consistent with output at potential and stable inflation. A nominal policy rate below expected inflation plus the neutral real rate is stimulative even if the headline number looks high; the same rate is restrictive if inflation has fallen. The neutral rate is unobservable and estimated, which is a permanent source of policy error.

The Taylor rule formalises the judgement: the prescribed nominal policy rate equals the neutral real rate plus current inflation, plus a weight on the gap between actual and target inflation, plus a weight on the output gap, with both weights conventionally set at one half. Because the inflation term appears twice, the rule prescribes a more than one-for-one rise in nominal rates when inflation overshoots, ensuring the real rate actually tightens.

Effective monetary policy rests on independence, credibility and transparency. An independent central bank can raise rates into an election year; a credible one anchors inflation expectations, so wage and price setters do not build past inflation into future contracts. Where credibility is weak, disinflation costs more output. The limits are equally examinable: at the effective lower bound conventional easing loses traction, a liquidity trap can leave money demand perfectly elastic, and monetary policy cannot fix supply-side shocks without imposing a demand contraction.

At Level I you should be able to classify a stance as expansionary or contractionary relative to neutral, compute a Taylor rule prescription, trace a rate change through the transmission channels to output, inflation and the currency, and assess the combined effect of a given monetary and fiscal policy mix on interest rates, the private-sector share of output and the exchange rate.