Monetary policy and the central bank

Monetary policy is how a central bank manages the supply of money and the cost of credit to keep inflation under control and, where its mandate allows, support employment and growth. It is the most powerful lever over financial markets.

The main tool: the policy rate

The headline instrument is the benchmark interest rate — the SELIC in Brazil, set every ~45 days by the Copom. By raising or lowering it, the central bank tightens or loosens the entire economy:

• Tightening (raising rates) — used to fight inflation. It cools borrowing, spending and demand. Tougher on stocks, supportive of the currency.
• Easing (cutting rates) — used to support a weak economy. It stimulates credit and risk-taking. Generally supportive of stocks.

Beyond the rate

Central banks have other tools: changing reserve requirements for banks, open-market operations (buying and selling government bonds), and in extreme cases quantitative easing — large-scale asset purchases to inject money when rates are already near zero.

Independence and credibility

A central bank's power rests on credibility. If markets trust it to defend its inflation target, expectations stay anchored and its job is easier. The Banco Central do Brasil gained formal autonomy in 2021, insulating its decisions somewhat from short-term political pressure — a change markets generally welcomed because it strengthens that credibility.

Why you watch it

Monetary-policy decisions and, just as importantly, the language of the accompanying statement (the "forward guidance") routinely move markets more than almost any other event. A rate hold paired with a hawkish tone can sell off stocks just as a surprise cut might rally them.