Monetary Policy

The Economy's Thermostat

Monetary policy is the central bank's management of interest rates and the money supply to keep inflation low and output stable. In the euro area that job belongs to the European Central Bank (ECB), whose primary mandate is price stability — inflation near 2%.

The main lever: the policy interest rate — the rate at which commercial banks borrow from the central bank. It ripples outward: bank funding costs → loan and mortgage rates → spending and investment decisions across the whole economy.

Expansionary policy (economy weak, inflation low): cut rates. Cheaper credit → more investment and consumption → demand and output rise.

Restrictive policy (inflation high): raise rates. Dearer credit cools spending → demand eases → price pressure fades. The medicine works by making the economy slightly ill on purpose.

How banks multiply money. Banks keep only a fraction of deposits as reserves and lend the rest; the loans return as new deposits and are lent again. With reserve ratio $r$, an initial deposit supports up to

$$\text{money multiplier} = \frac{1}{r}$$

times its value in total deposits. A 10% ratio turns 1,000€ of base money into up to 10,000€ of deposits — money is mostly lending, not printing.

Transmission lags. A rate change today reaches prices only after 6–24 months, so central banks steer by forecast, like turning a ship. It is why they speak carefully: expectations of future policy move markets before the policy itself does.

The two stances

Tip: Follow the transmission chain in order: policy rate → bank funding costs → loan and mortgage rates → spending and investment. Each link takes time — monetary policy acts with a lag of months, not days.

Common pitfall: Treating the money multiplier $1/r$ as a prediction. It is an upper bound — if banks hold excess reserves or borrowers stay away, actual money creation falls well short of it.