Quantitative Easing and Tightening
Buying or running off bonds to influence longer-term rates, used when the policy rate alone is insufficient. It affects the long end, which the funds rate reaches only indirectly.
MadStockAlerts Research · Updated August 28, 2026
What to take away
- Quantitative easing is central bank purchases of longer-dated securities; tightening is the reverse.
- It targets the long end of the yield curve, unlike the overnight policy rate.
- The mechanism operates partly through portfolio rebalancing and partly through signalling.
- Runoff is passive: maturing securities are simply not reinvested.
- The magnitude of the effect is genuinely contested among economists.
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Changing the Size of the Balance Sheet
QE is the Fed buying bonds when it cannot cut rates further, and QT is letting those holdings run off. Both work on long rates rather than short ones.
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Why it exists
The policy rate is an overnight rate and cannot go far below zero. When more easing is needed than that allows, the alternative is to buy longer-dated Treasuries and mortgage securities, which lifts their prices and lowers their yields directly.
It is therefore a tool for a specific circumstance: policy is already at its lower bound and conditions still need to loosen. That it became a routine instrument rather than an emergency one is a development of the last two decades rather than a permanent feature.
How it is thought to work
| Channel | Mechanism |
|---|---|
| Portfolio rebalancing | Removing duration from the market pushes investors into other assets, lifting their prices |
| Signalling | Large-scale buying communicates a commitment to keep policy easy |
| Liquidity | Adding reserves supports the functioning of markets under stress |
The size of each channel is genuinely contested among economists. The direction of the effect on yields is well documented; the magnitude, and how much is signalling rather than mechanics, is not settled.
The third channel is the least disputed and the least discussed. In March 2020 the immediate problem was that Treasury markets had stopped functioning, and large-scale purchases addressed that directly rather than through any expectations channel.
Tightening
Quantitative tightening is usually passive: securities are allowed to mature without reinvesting the proceeds, so the balance sheet shrinks on a schedule. Outright selling is possible and is used rarely, because it is more disruptive.
Runoff withdraws reserves from the banking system. The practical constraint is that nobody knows in advance how few reserves is too few, and the discovery of that level has historically been abrupt: money market rates spike, and the programme is paused.
Scroll the chart sideways to see all of it.
What to watch
The balance sheet size, the announced monthly runoff caps, and the composition between Treasuries and mortgage securities. All are published weekly, and the trajectory is more informative than any single week's figure.
Federal Reserve economic series available directly, so balance sheet and rate series can be read alongside market data.
Macro explorer — for membersWhat is actually bought, and from whom
The mechanics are less exotic than the name suggests. The Federal Reserve buys Treasury securities and agency mortgage-backed securities in the open market, from primary dealers, and pays for them by crediting reserve accounts. No physical money is printed and nothing is given to the government directly; an asset moves from one balance sheet to another and a reserve balance is created.
- The seller ends up holding reserves instead of a bond, which is a shorter-duration and more liquid asset.
- The quantity of duration held by the private sector falls, which is the channel most of the theory relies on.
- Bank reserves rise, which is not the same as deposits rising and is frequently reported as though it were.
- The Fed earns the interest on what it holds and remits its profits to the Treasury, which reverses when its funding cost exceeds its portfolio yield.
The last point produced an unusual situation when policy rates rose above the yield on a portfolio bought at low rates: the central bank was paying more on reserves than it earned on its assets, and remittances to the Treasury stopped. It is an accounting consequence rather than a solvency question, and it is regularly described as the latter.
The evidence, and the honest uncertainty
Quantitative easing is one of the least settled areas in monetary policy, and any account that presents its effects as established is overstating what is known. The difficulty is that it has always been deployed alongside other measures, in crises, so the counterfactual is unavailable.
| Claimed channel | The state of the evidence |
|---|---|
| Lowers long-term yields | The best supported, though estimates of the size vary by an order of magnitude |
| Signals a low policy rate for longer | Widely accepted, and difficult to separate from explicit guidance |
| Raises asset prices generally | Correlation is clear; the mechanism beyond the discount rate is disputed |
| Raises inflation | Weakly supported. Large programmes ran alongside persistently low inflation for a decade |
| Directly increases bank lending | Poorly supported. Reserves are not lent out in the way the phrase implies |
Tightening carries the same uncertainty in reverse, with an added asymmetry: purchases were made rapidly and reductions are made by letting securities mature without reinvesting, which is slow and passive. A balance sheet expanded in eighteen months can take years to reduce, and the reduction has never been carried to completion.