The sharp steepening of the US Treasury yield curve following the Federal Reserve's decision this week to leave interest rates unchanged has raised fresh concerns about the central bank's credibility and its willingness to take more decisive action against inflation.

Analysts say the combination of falling short-term Treasury yields and rising long-term yields suggests that investors are becoming increasingly skeptical that the Fed will raise interest rates again, despite Chair Kevin Warsh's insistence that policymakers "will not hesitate to act" if inflationary pressures persist.

An unusual move in the bond market

Immediately after the Federal Reserve announced its decision to leave interest rates unchanged, Treasury yields initially declined across the curve as investors welcomed the absence of an immediate rate hike.

That move quickly reversed.

Short-term Treasury yields continued to decline, while longer-dated yields climbed sharply, with the 30-year Treasury yield reaching its highest level in 19 years.

The result was a pronounced steepening of the yield curve, which many investors interpreted as a sign that markets are becoming less confident in the Federal Reserve's commitment to fighting inflation.

Zachary Griffiths, Head of Investment Grade and Macro Strategy at CreditSights, described the move as a "twist steepener," calling it "an unhealthy response" to the Fed's policy decision.

The trend continued during Thursday's session, with the gap between short- and long-term Treasury yields widening further, particularly between the two-year and 10-year maturities, as well as between the two-year and 30-year bonds.

Markets question the Fed's resolve

Chip Hughey, Managing Director of Fixed Income at Truist Wealth, said the move in the yield curve reflects a market belief that the Federal Reserve is not preparing to launch an aggressive rate-hiking cycle.

While that could be supportive for economic growth, he said, it also increases uncertainty about the central bank's ability to bring inflation back under control.

Financial conditions tighten without Fed action

Analysts believe one reason the Federal Reserve kept interest rates unchanged is that financial conditions have already tightened significantly without the need for additional policy action.

Fed Chair Kevin Warsh noted that financial markets have already done much of the work of tightening monetary policy by pushing both nominal and real Treasury yields higher as investors reacted directly to incoming economic data rather than relying on forward guidance from the central bank.

During July, the yield on the benchmark 10-year Treasury note rose about 25 basis points, marking its largest monthly increase since March.

Why did the yield curve steepen?

A steeper yield curve is often interpreted as a sign that markets expect lower interest rates in the future or see little need for additional policy tightening.

Under normal circumstances, a so-called "bear steepener" occurs when yields rise across the curve, with long-term yields increasing faster than short-term yields.

This time, however, the market experienced a much less typical pattern: short-term yields declined while long-term yields continued climbing, highlighting a sharp divergence in investor expectations for monetary policy.

Analysts also said the move reflected fading expectations that the Federal Reserve would either raise interest rates in July or deliver a strong signal that further tightening remained likely after geopolitical tensions intensified in the Middle East during the month.

Before the Fed meeting, markets had fully priced in a 25-basis-point rate hike by September, while the spread between two-year and 10-year Treasury yields narrowed by about five basis points during the week leading up to the meeting.

Questions over Fed credibility

Juneet Dhingra, Head of US Rates Strategy at BNP Paribas, said the steepening of the yield curve suggests that a significant portion of the Federal Reserve's anti-inflation credibility, strengthened after the June meeting, has now been eroded.

He argued that the absence of a clear message keeping additional rate hikes firmly on the table could further undermine market confidence in the central bank.

Nicolo Boccin, Co-Head of Global Fixed Income at Azimut Group, said investors were unsettled by the Fed's new communication approach, which relies on providing less forward guidance and has prompted markets to price greater long-term inflation risk into Treasury bonds.

Jobs report could determine the next move

Analysts believe next week's US nonfarm payrolls report for July will provide a critical test of current market expectations.

Griffiths said stronger-than-expected employment data could reinforce the view that the Federal Reserve should have raised interest rates this week, potentially leading to an even steeper yield curve.

On the other hand, weaker labor market data could trigger a sharp reversal in bond market pricing by easing concerns that the Federal Reserve is falling behind the curve in its fight against inflation.