When the Federal Reserve buys securities, it creates new money electronically and uses it to purchase Treasury bonds or mortgage-backed securities from banks and financial institutions. This increases the amount of cash reserves in the banking system, pushes bond prices up, drives interest rates down, and ripples outward into borrowing costs, stock prices, and consumer spending. It’s one of the most powerful tools the Fed has for stimulating the economy.
How the Purchase Actually Works
The Fed doesn’t print physical dollars to buy bonds. Instead, it credits the reserve accounts that commercial banks hold at the Federal Reserve. Think of these reserve accounts like checking accounts that banks maintain at the central bank. When the Fed buys $10 billion in Treasury bonds from a bank, it simply adds $10 billion to that bank’s reserve balance. The bonds move to the Fed’s portfolio, and the bank now has more cash on hand.
This is what people mean when they say the Fed “creates money out of thin air.” No tax revenue funds these purchases. The Fed has the unique authority to expand its own balance sheet by keystroke. As of early 2026, the Fed holds roughly $6.3 trillion in securities acquired through this process over the past decade and a half.
Why Bond Prices Rise and Interest Rates Fall
Bond prices and interest rates move in opposite directions. When the Fed enters the market as a massive buyer, it pushes bond prices up and yields (the effective interest rate on those bonds) down. This happens through a straightforward supply-and-demand mechanism: the Fed is removing a large chunk of bonds from circulation, leaving fewer available for private investors to buy. With less supply on the market, investors accept lower returns.
This effect doesn’t stay confined to the specific bonds the Fed purchases. When yields drop on Treasury securities, investors looking for better returns shift their money into corporate bonds, mortgage-backed securities, and other assets. That increased demand pushes yields down across the board. During the first round of large-scale purchases after the 2008 financial crisis, key announcements alone drove yields down by close to a full percentage point on Treasuries, mortgage-backed securities, and corporate bonds simultaneously.
The San Francisco Fed identified this as the most important channel: by reducing the overall supply of longer-term securities available to investors, the Fed pushes up prices and pushes down yields across the entire bond market.
How Lower Rates Reach the Real Economy
Lower long-term interest rates set off a chain reaction that touches nearly every corner of the economy. Corporate bond yields and mortgage rates are closely tied to Treasury yields, so when Treasury rates fall, businesses can borrow more cheaply to expand, and homebuyers get lower mortgage rates. The interest rate on car loans and other consumer borrowing also tends to decline.
The Fed’s own modeling shows these connections explicitly. Mortgage rates track the 10-year Treasury yield, consumer borrowing costs follow the 5-year yield, and stock valuations respond to the 30-year yield. When the Fed buys securities and compresses those yields, the effects fan out into business investment, home purchases, and household spending on big-ticket items.
There’s also a wealth effect. As bond yields fall, stock prices tend to rise because investors move money into equities seeking higher returns, and because lower borrowing costs make companies more profitable. Higher stock and home values make households feel wealthier, encouraging them to spend more freely. The dollar also tends to weaken modestly, which helps U.S. exports by making American goods cheaper overseas.
The Impact on Growth and Inflation
The real-world economic boost from security purchases is meaningful but not enormous. One Fed model estimated that a large-scale purchase program adds about 0.13 percentage points to real GDP growth, with the effect fading after roughly two years. The same model found that without the purchases, GDP growth would have been about 0.97% and core inflation about 0.77%, meaning the program prevented the economy from sliding closer to deflation.
That anti-deflation role may be the most underappreciated effect. During and after the 2008 crisis, the Fed’s purchases pushed inflation roughly a full percentage point higher than it otherwise would have been. That sounds alarming, but at the time the economy was flirting with deflation, a dangerous spiral where falling prices discourage spending and investment. The purchases helped keep inflation in a stable, positive range.
The mechanism works partly through psychology. When the Fed announces large purchases, it signals to markets that it intends to keep short-term interest rates low for an extended period. That expectation alone can push long-term rates down before the Fed even completes its buying, because investors price in a longer period of cheap borrowing.
Standard Operations vs. Quantitative Easing
The Fed has always bought and sold securities as part of routine monetary policy. Before the 2008 crisis, these open market operations were relatively small and focused on short-term securities. The goal was narrow: adjust the supply of bank reserves to keep the overnight lending rate between banks near the Fed’s target.
Quantitative easing (QE) is a different animal. It involves purchasing much larger volumes of longer-term securities, specifically to push down long-term interest rates when short-term rates have already hit zero and can’t go any lower. The Fed ran multiple rounds of QE between late 2008 and October 2014, expanding its balance sheet from under $1 trillion to over $4 trillion. The scale and the focus on long-dated bonds are what distinguish QE from the Fed’s everyday operations.
What Happens When Purchases Stop
The reversal process, often called quantitative tightening, is deliberately slow. Rather than selling bonds back into the market all at once (which could spike interest rates and rattle markets), the Fed typically lets its holdings shrink gradually. When a bond in its portfolio matures, the Fed simply doesn’t reinvest the proceeds. The money effectively disappears from the system, reversing the creation process.
The Fed has stated it intends to reduce its holdings “in a predictable manner” by adjusting how much of the maturing principal it reinvests. It plans to slow and then stop this runoff once bank reserves drop to a level it considers “ample” for the financial system to function smoothly. Even after active runoff stops, reserves continue declining for a time as other Fed liabilities grow, until balances settle at the target level. From that point, the Fed manages its holdings to maintain enough reserves in the system.
This process can take years. The pace matters because draining reserves too quickly can cause disruptions in overnight lending markets, where banks and financial institutions borrow from each other on a daily basis. The Fed maintains standing lending facilities specifically to prevent these short-term funding markets from seizing up during the transition.
Who Benefits and Who Doesn’t
Security purchases broadly benefit borrowers and asset owners. If you’re taking out a mortgage, refinancing a loan, or running a business that needs capital, lower rates reduce your costs. If you own stocks or real estate, rising asset prices increase your wealth.
Savers and retirees on fixed incomes are on the other side of the equation. Lower yields mean savings accounts, CDs, and newly purchased bonds pay less. Pension funds and insurance companies that rely on bond income to meet future obligations also face pressure, sometimes needing to take on more risk to hit their return targets. This tension between stimulating the broader economy and squeezing savers is one of the most debated trade-offs of large-scale asset purchases.