Why this one is basically cash
The 3-month Treasury yield is the shortest, safest, most liquid dollar asset in the world. When a money market fund says it holds "cash equivalents," this is what's in there. When an institutional treasurer says their firm is "in T-bills," this is the instrument. It's boring on purpose — and that boringness is exactly what makes it useful.
Technically, the 3-month yield references the 13-week Treasury bill, which is a discount instrument. You don't earn interest along the way; you buy it below face value and it matures to par. Bills are auctioned weekly, held to maturity by most buyers, and rarely traded actively. Yahoo Finance publishes the yield under the ticker ^IRX, which is what powers the live widget at the top of this page.
The Fed's shadow
Here's the important thing to understand about the 3-month yield: it's not really a forecast of anything. It's just what the Fed is doing right now, reflected in a tradable instrument. The 3-month tracks the federal funds rate almost perfectly — usually within 10 to 20 basis points — because arbitrage forces them into alignment. If the 3-month yielded meaningfully more than Fed funds, banks would simply borrow in the funds market and buy T-bills for a riskless profit. That pressure keeps the two rates glued together.
Practically, this means the 3-month is the cleanest proxy available for current monetary policy. It's not about what the Fed will do — that's the job of the 2-year and longer maturities. It's about what the Fed is doing, today, in the real world.
What moves it
Because it's so tightly tied to current policy, the 3-month doesn't move as much as longer-duration yields. The things that do move it are:
- Fed target rate changes. This is the overwhelming driver. When the Fed hikes or cuts by 25 basis points, the 3-month usually moves by almost exactly the same amount within days.
- Forward guidance. If the Fed signals an imminent change (say, "we're likely to cut at the next meeting"), the 3-month starts pricing it in before the actual decision.
- Liquidity stress. When dollar funding markets get weird — as they did in the 2019 repo spike, or briefly in March 2020 — T-bills can decouple from Fed funds and trade at unusual yields.
- Treasury bill supply. When the Treasury issues more bills than usual (for example, after a debt ceiling standoff), yields can drift higher temporarily to absorb the new supply.
- Quarter-end and year-end flows. Banks and money market funds rebalance around these dates, which can cause small technical moves in bill yields.
What it means for your savings
If you have money sitting in a high-yield savings account, a money market fund, or a short-term CD, what you earn is essentially the 3-month Treasury yield minus a fee. When the 3-month is at 5%, the best Treasury money market funds pay roughly 4.8–4.9%. Your bank's savings account probably pays a lot less — that gap is the bank's profit margin, and you're paying it by leaving your money there instead of in a T-bill fund or directly in bills.
A rough rule of thumb: if your savings account is paying more than 1 percentage point below the 3-month yield, you're getting a bad deal. The difference compounds fast on larger balances.
A short history
The 3-month Treasury yield tells a simpler story than longer-dated yields. For most of the post-WWII era, it ran in the 2% to 6% range, moving with Fed policy cycles. In the Volcker years of the early 1980s, it spiked above 15%. In the post-2008 era, it spent seven years pinned at essentially zero as the Fed kept rates at the lower bound. It returned to near-zero during the COVID crisis in 2020, and then climbed rapidly — from roughly 0% in early 2022 to above 5% by mid-2023 — as the Fed fought the inflation shock.
Where it sits today depends entirely on where the Fed is. Unlike the 10-year, which embeds complex forecasts about the next decade, the 3-month is just a real-time readout of current monetary policy. Which is exactly why it's the cleanest "cash rate" reference point available.