Between 2009 and 2022, the world's major central banks collectively purchased over $20 trillion of financial assets. This unprecedented intervention — quantitative easing — reshaped bond markets, compressed yields across every asset class, inflated asset prices, and became one of the most consequential and debated policies in modern economic history. Understanding QE means understanding both how it works and where its limits lie.
Why QE works (in theory)
When a central bank buys £100 billion of government bonds from pension funds, insurance companies, and banks, several things happen simultaneously. First, the sellers receive cash — newly created central bank reserves — in exchange for bonds. These reserve holders now have more cash and less bonds than they want, so they invest elsewhere: in corporate bonds, equities, or other assets. This "portfolio balance channel" pushes up asset prices and pushes down yields across the board. Second, long-term bond yields fall directly because the central bank is a large buyer, increasing bond prices. Lower long-term yields reduce borrowing costs for households and businesses. Third, the signal effect: the central bank demonstrates its commitment to accommodative policy, lowering expectations for future rates.
QE and the wealth effect
The most documented and most criticised effect of QE was the inflation of asset prices. When QE pushes bond yields near zero, investors seeking returns move into equities, property, and other risk assets. This drove major stock market recoveries after 2009 and 2020, and contributed to sharp rises in house prices across advanced economies. The problem: those who own financial assets (disproportionately wealthier households) benefit directly from this price inflation, while those without assets see little benefit but may face higher housing costs. QE has therefore been widely criticised for worsening wealth inequality — a charge central banks acknowledge but dispute in terms of the counterfactual (the alternative being recession and higher unemployment).
Quantitative tightening: the reversal
The exit from QE — quantitative tightening (QT) — involves the central bank allowing bonds to mature without reinvesting the proceeds, or actively selling bonds back to the market. QT withdraws reserves from the banking system and puts upward pressure on long-term yields. The challenge: QT in 2022–2023 coincided with the fastest interest rate hiking cycle in decades, creating simultaneous upward pressure on rates at all maturities. Markets became less liquid, and the UK gilt market experienced a severe dysfunction in September 2022 that forced the Bank of England to temporarily suspend its own QT programme and resume bond buying — a striking demonstration of how dependent market functioning had become on central bank participation.