US inflation keeps Fed rates higher for longer

US inflation rose to 3.7% in September, driven largely by energy prices amid geopolitical tensions around the Iran conflict, according to the data context. Core inflation, which strips out food and energy, also remained elevated at 0.33% on a monthly basis in the latest read, reinforcing the view that underlying price pressures are not yet back at the Fed’s 2% target. Inflation has now run above that goal for more than five years, leaving policymakers with little room to declare victory.

That backdrop has already moved markets. The 10-year Treasury yield climbed to 5.21% on Oct. 13 before easing slightly, while the iShares 20+ Year Treasury Bond ETF, TLT, remains under pressure even after a brief rebound, closing at 80.05 on Oct. 16, below its 200-day moving average of 83.4. The ETF’s RSI has recovered to 67.9, but the broader trend still reflects fragile demand for long-duration bonds. In credit and rates markets, the jump in yields underscores the risk that the Fed is being pulled toward a more hawkish stance just as investors had been looking for policy relief.

Equities are also feeling the strain. The S&P 500 and Russell 2000 both sold off sharply in recent sessions before stabilizing, suggesting that hotter inflation is forcing a repricing of both growth and financing assumptions. Small caps, which are typically more sensitive to funding costs, have been hit harder than large caps, a sign that the market is reducing exposure to domestically leveraged names that would suffer most from another leg up in rates.

Kapteyn’s warning also has implications beyond the Fed. Higher yields strengthen the dollar, tightening financial conditions globally and adding pressure to economies already struggling with weak growth, from Europe to parts of Asia. For corporates, especially those dependent on refinancing or floating-rate borrowing, every additional rate hike raises the cost of capital and can delay investment decisions. At the same time, persistent inflation can support revenues in some sectors, but only if demand holds up; otherwise margins get squeezed as consumers absorb higher prices.

For investors, the key question is whether the latest inflation burst proves temporary, driven by energy and geopolitics, or whether it feeds into wages and services and keeps the Fed on alert into 2027. Adalytica’s confidence gauge on the Fed’s 2% inflation target has jumped sharply, while Treasury-bond sentiment has swung to what its models classify as extreme greed, reflecting heavy defensive positioning and expectations for continued volatility. If inflation stays hot, the market’s base case for a pause-and-cut cycle could give way to a more punitive “higher for longer” path.

The next catalyst is whether upcoming inflation and labor data confirm that September was an energy-driven spike or the start of a broader re-acceleration. If it is the latter, Kapteyn’s warning about hikes beyond December may quickly shift from a tail risk to the central scenario.