When the Federal Reserve buys Treasury securities in the open market, it injects money into the banking system. This increases the supply of reserves, lowers the federal funds rate, and generally reduces short-term interest rates across the market. In contrast, increasing reserve requirements or selling securities would tighten the money supply, pushing interest rates up, not down.

A reverse repurchase agreement (reverse repo) involves the Fed selling securities with an agreement to buy them back later. This drains liquidity from the banking system and tends to raise short-term interest rates. To lower rates, the Fed would more likely buy securities (open market purchases) or lower the offered rate on reverse repos, both of which inject liquidity and push rates down.

The IORB rate serves as a floor for the federal funds rate. If the Fed lowers the interest it pays on excess reserves, banks are less inclined to hold reserves and more likely to lend them out, increasing the supply of funds in the interbank market and reducing short-term interest rates. Raising the IORB or the target rate would do the opposite.

When the Fed sells Treasury securities in the open market, it pulls money out of the banking system, reducing reserves and tightening the money supply. This leads to higher interest rates, discouraging borrowing and spending, and thereby reducing aggregate demand—a key goal when trying to combat inflation. Buying securities would have the opposite effect and increase aggregate demand.

The neutral interest rate (also called the natural or equilibrium rate) is the rate at which monetary policy is neither expansionary nor contractionary. It’s typically estimated as the sum of the trend rate of real economic growth and the inflation target. If the policy rate is below the neutral rate, monetary policy is considered expansionary—stimulating growth. If it is above, the policy is contractionary, aimed at slowing inflation or overheating.

Most modern central banks—including the Federal Reserve, European Central Bank, and Bank of England—use inflation targeting as their primary monetary policy framework. This approach involves setting an explicit inflation goal, typically around 2%, and adjusting policy tools (like interest rates and asset purchases) to maintain price stability. While interest rate adjustments are a key instrument, it’s the inflation rate that serves as the central target guiding those decisions.

In a liquidity trap, interest rates are already near zero, and people expect deflation or stagnant growth. As a result, they hoard cash instead of spending or investing, making monetary stimulus ineffective. Even though central banks expand the money supply, it doesn't translate into higher demand or inflation. This is distinct from bond market reactions or inelastic money demand, which don’t fully explain persistent deflation under loose monetary conditions.

Japan is a textbook example of a liquidity trap. Even with zero interest rates and expanded money supply, businesses and consumers chose to save rather than spend, anticipating continued deflation and uncertainty. In such cases, traditional monetary tools lose effectiveness because people prefer liquidity over investment or consumption. This explains why Japan's policies did not generate inflation or robust growth, despite their expansionary intent.

Despite the ECB's efforts, the transmission mechanism of monetary policy broke down in some Eurozone countries. Deep recessions and weak bank lending created conditions resembling a liquidity trap, where households and firms hoarded cash amid uncertainty. Inflation remained well below target, and monetary stimulus had minimal impact on actual demand.

Most central banks today use inflation targeting as their primary monetary policy framework. This approach involves setting a publicly announced inflation rate—typically around 2%—as the main goal, and adjusting policy tools (such as interest rates) to keep inflation near that target. Money supply targeting was more common in earlier decades but has become less reliable due to instability in money demand. Exchange rate targeting is still used by some countries but is far less widespread than inflation targeting.