Monetary Policy: IB Economics 3.5 notes

What monetary policy is and who runs it

A central bank, such as the US Federal Reserve, the European Central Bank, or the Bank of England, conducts monetary policy: it adjusts the policy interest rate and the money supply to influence aggregate demand. Most central banks are operationally independent from the government, so decisions are not driven by the electoral cycle. Their main goal is usually price stability, expressed as an inflation target, alongside supporting employment and steady growth.

The policy rate is the interest rate the central bank charges commercial banks or pays on their reserves. Because it anchors the whole structure of borrowing and saving rates in the economy, moving it even a fraction of a percentage point ripples out to mortgages, business loans, and savings accounts.

The transmission mechanism, step by step

Suppose a central bank cuts its policy rate to stimulate a weak economy. Step one: commercial banks lower the rates they charge on loans and pay on deposits. Step two: cheaper borrowing and a smaller reward for saving encourage households to spend, especially on interest-sensitive items like cars and housing, so consumption (C) rises. Step three: the lower cost of borrowing makes more investment projects profitable, so firms' investment (I) rises. Step four: aggregate demand, C + I + G + (X - M), shifts right, raising real output and the price level.

A fifth channel works through the exchange rate. Lower interest rates tend to reduce financial inflows, weakening the currency; a weaker currency makes exports cheaper abroad and imports dearer, so net exports rise, adding further to aggregate demand. You can build and drag each of these steps in the money market at /sandbox/monetary-policy, and the monetary policy walkthroughs at /graph-walkthroughs trace the effect across 1-year, 5-year, and 10-year horizons, including how money is neutral in the long run.

Expansionary vs contractionary policy

Expansionary (loose) monetary policy lowers interest rates and expands the money supply to raise aggregate demand when the economy is below full employment or in recession. Contractionary (tight) monetary policy raises rates and slows money growth to cool an overheating economy and bring down demand-pull inflation.

Quantitative easing (QE) is an unconventional expansionary tool. The central bank creates money to buy government bonds and other assets, pushing up their prices and lowering long-term interest rates when the policy rate is already close to zero.

Real vs nominal interest rates

Central banks set nominal interest rates, but borrowing and saving decisions depend on the real interest rate, which is roughly the nominal rate minus the inflation rate (the Fisher relationship). If a bank charges a nominal 5% while inflation is 3%, the real cost of borrowing is only about 2%.

This matters for policy. During high inflation a seemingly high nominal rate can still be low or negative in real terms, meaning policy is looser than it looks. Argentina in the early 2020s ran nominal rates above 100% while inflation ran even higher, so real rates were deeply negative for long stretches.

Inflation targeting

Most modern central banks pursue an explicit inflation target: 2% CPI at the Bank of England and the ECB, a 2% average target at the Federal Reserve, and 4% with a plus-or-minus 2% band at the Reserve Bank of India. A public target anchors expectations, so workers and firms build roughly the target rate into wage and price setting, which itself helps keep inflation stable.

Strengths and limitations

Strengths: interest-rate decisions can be taken quickly and adjusted in small increments; central bank independence insulates them from political pressure; and the changes are incremental and reversible.

Limitations: monetary policy works with long and variable time lags of up to 18 to 24 months; it is a blunt tool that cannot target specific regions or sectors; and banks may not pass on cuts, while pessimistic households may not borrow even when rates are low. It is also poorly suited to cost-push inflation, where cooling demand would deepen a downturn.

The liquidity trap

When nominal interest rates fall to near zero the central bank hits the zero lower bound, and further cuts become impossible or ineffective. In a liquidity trap households and firms prefer to hold cash rather than spend or lend, so extra money injected by the central bank is hoarded and aggregate demand does not respond. Japan spent much of the 1990s and 2000s in this position, which is why economists often argue that fiscal policy or QE must take over when monetary policy is trapped.

How this is examined

• Monetary policy is a favourite Paper 1 part (b) essay: examiners reward a clear step-by-step transmission mechanism (rate to C, I, and net exports to AD) rather than just asserting that AD rises.
• For evaluation marks, weigh strengths (speed, independence) against limitations (time lags, liquidity trap, blunt tool) and finish with a supported judgement about circumstances, for example that policy is weak at the zero lower bound.
• Do not confuse the interest rate with inflation: state the Fisher link (real equals nominal minus inflation) if a question gives you both figures.

Key terms

central bankinterest rateaggregate demandreal interest rateliquidity trapquantitative easing