Central banks, interest rates and liquidity: QE and QT

No single institution moves markets like a central bank. It sets the price of money, and through its balance sheet it changes how much money is in the system. Both feed straight into asset prices.

What central banks are trying to do

The Bank of England targets 2% inflation. The Federal Reserve has a dual mandate: stable prices (also 2% inflation) and maximum employment. The ECB focuses on price stability for the euro area. Rates are set by committees: the BoE’s Monetary Policy Committee and the Fed’s FOMC each meet eight times a year.

Tool one: the policy rate

The central bank sets a short-term interest rate (Bank Rate in the UK, the fed funds target range in the US). It ripples outwards:

Borrowing costs: mortgages, business loans and credit cards reprice.
Savings: higher rates make cash and bonds more attractive versus stocks.
Currency: higher rates tend to attract capital and strengthen the currency.
Valuations: as covered in lesson 1.9, higher rates lower the present value of future cash flows.

Hiking slows the economy to bring inflation down. Cutting supports growth. Policy works with long and variable lags, often a year or more, so central banks act on forecasts, not just current data.

Forward guidance

Markets price expected rate moves well in advance, so what a central bank signals about the future often moves markets more than the decision itself. The statement, the press conference, the vote split and the projections (such as the Fed’s “dot plot”) are all read line by line. A cut that was fully expected can still trigger a sell-off if the guidance is less dovish than hoped.

Tool two: the balance sheet

When rates hit zero in 2008 and again in 2020, central banks needed another lever.

Quantitative easing (QE): the central bank creates new reserves and uses them to buy government bonds (and sometimes other assets). That pushes bond prices up and yields down, lowers borrowing costs across the economy and floods the financial system with liquidity. Investors who sold bonds now hold cash, which tends to flow into riskier assets.

Quantitative tightening (QT): the reverse. The central bank lets bonds mature without reinvesting, or sells them outright, as the BoE has done. Reserves shrink and liquidity is drained.

Shape of the Fed balance sheet (not to scale): QE expands it, QT shrinks it.

The Fed’s balance sheet grew from under $1 trillion before 2008 to nearly $9 trillion in 2022, then shrank through QT before the Fed ended QT on 1 December 2025.

Liquidity and asset prices

Rising liquidity has tended to coincide with rising asset prices, especially the most speculative ones. 2020 to 2021 (QE plus zero rates) saw surging tech, crypto and SPACs. 2022 (rapid hikes plus QT) saw most of them fall sharply. Correlation isn’t a perfect rule, but liquidity is one of the most important tides markets swim in.

Professionals watch more than the headline balance sheet. In the US, bank reserves, the Treasury’s cash account (the TGA) and the reverse repo facility all affect how much liquidity is actually available to markets.

When it goes wrong

In September 2022, the UK mini-budget sent gilt yields soaring. Pension funds using leveraged liability-driven investment (LDI) strategies faced margin calls and had to sell gilts, pushing yields higher still. The Bank of England stepped in with temporary gilt purchases, even while it was trying to tighten policy. It’s a clear example of the central bank acting as a lender and buyer of last resort to stop a market spiral.

Key takeaway

Rates set the price of money, the balance sheet sets the quantity. Watch both, and watch what central banks say about the future as closely as what they do.

Educational content only, not financial advice. Investing involves risk and you can lose money.

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