Yield Curve Flattens as 2-Year Treasury Jumps Around Fed Hike

WASHINGTON — The Treasury yield curve flattened sharply in the first three weeks of September 2026, according to the Treasury Department’s daily par yield curve data, as short-term yields climbed into and through the Federal Reserve’s September 16 decision to raise interest rates. From September 1 to September 18, the 2-year Treasury yield rose 37 basis points while the 10-year Treasury gained 22 and the 30-year just 7.

The numbers

On September 1, the par yield curve showed the 3-month bill at 3.92 percent, the 2-year note at 4.39 percent, the 5-year at 4.55 percent, the 10-year at 4.79 percent and the 30-year bond at 5.27 percent. By September 18, the 3-month stood at 4.14 percent, the 2-year at 4.76 percent, the 5-year at 4.86 percent, the 10-year at 5.01 percent and the 30-year at 5.34 percent.

The spread between the 10-year and 2-year yields, a widely watched gauge of the curve’s slope, narrowed from 40 basis points to 25 over that span. The gap between the 30-year and the 2-year compressed from 88 basis points to 58.

Much of the move came in a single stretch. Between September 8 and September 11, the 2-year yield rose from 4.39 percent to 4.63 percent, and the 1-year from 4.15 percent to 4.35 percent, as markets moved to price a rate increase at the following week’s meeting.

Around the decision

On September 16, the Federal Open Market Committee raised the target range for the federal funds rate by a quarter point to 3.75 to 4.00 percent, in a unanimous vote, saying the move would support a timelier return to its 2 percent inflation goal. That day, the par curve showed the 2-year at 4.74 percent and the 10-year at 5.01 percent, giving a 10-year to 2-year spread of 27 basis points.

The day after the decision, yields dipped across most maturities, with the 2-year falling to 4.67 percent and the 10-year to 4.94 percent. By September 18 they had more than retraced the move, with the 2-year at 4.76 percent and the 10-year back at 5.01 percent.

A yield curve with a kink

The data also show an unusual feature at the long end. From September 10 onward, the 20-year yield sat above the 30-year, after the two had matched on several days earlier in the month. On September 16 the 20-year was at 5.39 percent against 5.35 percent for the 30-year, and on September 18 at 5.38 percent against 5.34 percent. That inversion between the two longest points on the curve has been a recurring feature of the Treasury market and is often attributed to the 20-year’s relatively thinner liquidity.

What the flattening says

The pattern is a textbook bear flattening: yields rising across the curve, but most at the front end. It typically occurs when markets reprice the near-term path of monetary policy higher while longer-term growth and inflation expectations change less. In other words, investors were treating the Fed’s move as a response to current inflation rather than a sign that inflation would remain elevated for years.

That reading fits the Fed’s own projections released the same day, in which the median participant saw PCE inflation falling from 3.7 percent in 2026 to 2.3 percent in 2027. If the bond market shares that outlook, there is limited reason for 30-year yields to rise in step with the 2-year.

There is a cost, though. A 10-year Treasury yield at or above 5 percent sets a high floor for mortgage rates and corporate borrowing costs, even if the curve is flatter. The flattening means the policy-sensitive front end has done most of the adjusting, but the long end remains at levels that keep financing costs elevated across the economy.

What to watch

The next tests are the late-September 2-, 5- and 7-year note auctions, which will show how much demand exists at the new, higher short-term yields, and the incoming inflation and payroll data. A further narrowing of the 10-year to 2-year spread toward zero would suggest markets expect the Fed to keep tightening; a re-steepening would suggest investors see the September increase as a one-time adjustment.