QE, QT and How Central Banks Move Bonds

Beyond the Policy Rate

Most people know that central banks set interest rates. What's less understood is that the overnight policy rate — the rate banks charge each other for very short-term loans — is only one lever. It directly controls the very short end of the borrowing market. But mortgages, corporate loans, and government debt with maturities of ten or thirty years are priced off something else: long-term bond yields. Moving those requires different tools.

That's where the balance sheet comes in. A central bank's balance sheet lists what it owns (assets, mainly bonds) and what it owes (mainly the currency it has issued). Expanding it means buying bonds. Shrinking it means letting bonds mature without replacement, or actively selling them. These balance-sheet operations are the subject of this guide. For a broader look at how interest-rate decisions are made, that guide covers the meeting-by-meeting mechanics.

What Is Quantitative Easing?

Quantitative easing — almost always shortened to QE — is when a central bank creates new money electronically and uses it to buy bonds, typically government bonds, directly in the financial markets. The central bank's asset pile grows; the sellers (usually banks and investment funds) receive newly created reserves in return. "Quantitative" just refers to the fact that the central bank is targeting a quantity of assets to buy, not just a price.

The mechanical effect on bonds is straightforward. When a large buyer enters the market and purchases a huge volume of bonds, it pushes bond prices up. Because bond prices and yields move in opposite directions, rising prices mean falling yields. Lower long-term yields make borrowing cheaper across the economy — for governments, companies issuing debt, and households taking out mortgages.

Why Normal Rate Cuts Sometimes Aren't Enough

Central banks typically reach for QE when the policy rate has already been cut to near zero and can't go much lower. At that point, the short end of the yield curve is pinned, but longer-term yields may still be elevated enough to dampen borrowing and investment. QE is the tool designed to reach further along the curve.

The 2008 global financial crisis was the first major deployment of modern QE by the US Federal Reserve and the Bank of England. Credit markets had frozen, and conventional rate cuts alone weren't moving long-term borrowing costs fast enough. The Fed began purchasing large quantities of Treasury bonds and mortgage-backed securities (bundles of home loans packaged as tradeable bonds). The 2020 COVID-19 shock triggered an even faster and larger round of QE, with central banks around the world acting within days of market disruption rather than months.

How QE Moves the Yield Curve

The yield curve is a snapshot of yields across different maturities — say, two-year, five-year, and ten-year government bonds — plotted from left to right. Normally it slopes upward, because lending money for longer feels riskier and lenders demand more compensation. QE specifically targets the middle and long end of that curve.

Central banks can also signal that rates will stay low for a long time — a practice called forward guidance. This presses down yields further by reducing investors' expectations of future rate rises. QE and forward guidance tend to work together: the purchases suppress yields mechanically, while the guidance anchors expectations.

One important nuance: QE doesn't eliminate the term premium — the extra yield investors demand for locking up money for longer periods. It compresses it. Historically, economists have found that large QE programs can move long-term yields by meaningful amounts, but the precise effect depends on the size of purchases, the state of the economy, and how much uncertainty exists in markets at the time.

What Is Quantitative Tightening?

Quantitative tightening, or QT, is the reverse process. The central bank allows bonds on its balance sheet to mature (reach their repayment date) without using the returned cash to buy new bonds. This is called "passive" or "runoff" QT. In a more active version, the central bank sells bonds outright before they mature, which removes money from the system even faster.

The balance-sheet effect is the mirror image of QE. Fewer central bank purchases — or active selling — means less demand for bonds. All else equal, that nudges bond prices down and yields up, adding upward pressure to longer-term borrowing costs. Traders typically watch the pace of QT closely because even modest changes to the schedule can shift government bond yields at the longer end of the curve.

Passive Runoff vs Active Sales

Most central banks have preferred passive runoff as a gentler, more predictable approach. Active sales are rarer precisely because they can move markets more abruptly. The Federal Reserve used capped runoff after both the post-2008 and post-2020 QE cycles, announcing in advance how much it would allow to roll off each month so that markets could adjust gradually.

Transmission: From Central Bank to Economy

The chain of effects that runs from a central bank's decisions to real-world borrowing costs is called the transmission mechanism. Understanding it explains why economists watch central bank balance sheets as closely as policy-rate announcements.

1. Policy rate → short-term rates. The overnight policy rate sets the floor for very short-term borrowing. Banks pass it on to each other and, eventually, to customers through savings accounts and short-term loans.
2. QE/QT → long-term yields. Balance-sheet operations push long-dated government bond yields up or down, independently of where the overnight rate sits.
3. Long yields → mortgage rates. Home loans are typically priced relative to long-term government bond yields — in the US, often the 10-year Treasury. When that yield falls, fixed mortgage rates tend to follow.
4. Long yields → corporate borrowing costs. Companies that issue bonds (corporate bonds) price their debt at a credit spread above government yields. If government yields fall, corporate borrowing costs tend to fall too, making it cheaper for businesses to invest or refinance existing debt.
5. Cheaper borrowing → spending and investment. Households can afford larger mortgages or cheaper car loans. Companies can invest in equipment or hire staff at lower funding costs. Economists read this as the intended stimulative effect of easing.

The same chain runs in reverse during tightening. Rising long yields make mortgages more expensive, slow corporate borrowing, and can cool asset prices — all of which reduce spending and, in theory, bring inflation down.

Reading Central Bank Signals on the Bond Market

Markets watch several signals to anticipate balance-sheet shifts. Central bank meeting statements, minutes, and speeches by senior officials often telegraph whether QE might be "tapered" (gradually wound down) or whether QT will accelerate. The word "taper" became famous in 2013 when a hint that the Fed might slow its bond purchases caused yields to spike sharply — a period that became known as the "taper tantrum."

The economic calendar is a good place to track central bank meeting dates and scheduled policy announcements. Changes in language around bond purchases can be just as significant as changes in the policy rate itself. Traders typically parse phrases like "at least at the current pace" (suggesting no change soon) versus "adjusting the pace as appropriate" (suggesting flexibility to reduce or increase purchases).

Volatility in bond markets often spikes around these announcements, particularly when the central bank's message surprises relative to what markets had priced in. The relationship between policy statements and bond yields is covered in more depth in the government bond yields guide.

What This Means for the Yield-Curve Shape

Because the policy rate dominates the short end of the curve and QE/QT influences the long end, a central bank can in principle reshape the curve, not just shift it up or down in parallel. If the policy rate is raised sharply while QE is still running (or QT has not yet begun), the short end rises faster than the long end, which can flatten or even invert the curve. An inverted yield curve — where short-term yields exceed long-term yields — has historically preceded recessions, though economists debate how much of the inversion signal survives in an era of large central bank balance sheets.

For a deeper look at what curve shapes mean and how markets read them, see the guide on the yield curve and its companion on yield-curve inversion. Understanding how central banks' balance-sheet decisions feed into the curve shape is increasingly central to reading the bond market in the modern era.