After completing a rate hike in September, the Federal Reserve was immediately confronted with an inflation report that gave policymakers little comfort, as the core CPI month-over-month gain held at 0.3% for a second consecutive month, significantly above the market expectation of 0.2%, directly shaking the market consensus of "pausing rate hikes to observe the effects of prior tightening."
Although headline prices were heavily influenced by energy price volatility, core inflation excluding food and energy failed to cool as expected and instead showed stronger stickiness, greatly compressing the Fed's policy options at its October meeting.
Prominent economist Gianluca Benigno pointed out in his latest analysis that the release of the September CPI data not only strengthened the case for further rate hikes but also made the October Federal Open Market Committee meeting a potential window for tightening action, with the market's focus shifting from "whether to pause" to "whether underlying inflation is still declining."
A deeper breakdown of the data structure shows that the rebound in core inflation was not caused by a single factor but by multiple forces reinforcing each other.
Core CPI rose 2.6% year-over-year, not only above the market expectation of 2.5% but also up from 2.4% in August; on a seasonally adjusted basis, it rose 0.3% month-over-month, unchanged from August and exceeding the 0.2% market expectation for two consecutive months.
Headline CPI rose 3.7% year-over-year and 0.6% month-over-month on a seasonally adjusted basis, with gasoline prices surging 9.1% month-over-month, contributing more than half of the monthly gain in headline CPI and highlighting that energy remains the primary force pushing overall prices higher.
However, the coexistence of surging energy prices and stubborn core inflation makes the policy implications of this report lean even more toward tightening.
Even temporarily excluding oil price volatility, the pace of increase in other consumer prices has not slowed to the extent the market had hoped.
The rise in core CPI year-over-year from 2.4% to 2.6% requires careful interpretation.
According to Benigno's calculations, the unrounded year-over-year gain actually rose from about 2.45% to 2.56%, an increase of roughly 0.11 percentage points rather than the 0.2 percentage points shown on the surface.
The low base from the same period last year amplified the change in the year-over-year reading, so one cannot conclude solely from the published figure's increase that core inflation suddenly accelerated sharply.
What truly affects policy judgment is the monthly trend: the slowdown the market expected did not occur, and the 0.3% month-over-month core CPI gain appeared once again.
Although this alone is not enough to confirm a new inflation upcycle, it means the Fed still lacks evidence to comfortably pause rate hikes.
Data compiled by Woofun AI shows that under the combined effects of the energy shock and base effects, the month-over-month resilience of core inflation has become a key variable constraining any policy pivot, and any strategy that seeks to wait for inflation to decline on its own appears insufficiently supported in the current data environment.
On structural pain points, the stagnation in housing inflation and the strengthening of non-housing services prices constitute the main sources of core inflation stickiness.
Previously, the gradual decline in housing inflation was seen as an important force driving core inflation lower, but in September this process clearly stalled.
Housing prices rose 3.2% year-over-year, up from 3.0% in August, and the seasonally adjusted month-over-month gain rose from 0.3% to 0.4%, contributing about half of the month's core CPI increase.
Among these, owners' equivalent rent — the estimated value of rental services provided by owner-occupied housing — rose 0.3% month-over-month, up from 0.2%; the gain in primary residence rent remained at 0.2%.
The year-over-year strengthening in housing was partly affected by a low base, but the acceleration in the seasonally adjusted month-over-month figure indicates that recent price trends have indeed changed.
For the Fed, this means the component that was expected to continue pulling core inflation lower has temporarily failed to play its expected role.
Beyond housing, services prices also remained resilient.
Core services prices excluding housing, often called "super core" services prices, rose 3.2% year-over-year, up from 3.1%, while the seasonally adjusted month-over-month gain held at 0.3%.
Transportation services rose 0.6% month-over-month, with airline fares up 1.2%; hospital services and education services rose 0.7% and 0.6%, respectively.
Benigno believes that the strength in transportation services prices suggests higher energy costs may be beginning to pass through to some services prices.
However, healthcare, education, and housing each have different price drivers, and these gains cannot all be attributed to oil prices.
In the goods sector, some relatively moderate signals remain.
Core goods prices rose 0.7% year-over-year in September, unchanged from August; apparel rose 3.4% year-over-year, down from 3.6%.
Although the seasonally adjusted month-over-month gain in core goods rose from 0.1% to 0.3%, there are not yet signs of broad acceleration in year-over-year gains.
This means the more accurate description at present is that core inflation stickiness has strengthened, rather than that all sectors have entered a broad price increase, and the policy difficulty lies in the fact that energy pressure has not faded while housing and other services have also failed to provide sufficient cooling force.
At the level of policy inference, the Fed already raised rates by 25 basis points at its September meeting, lifting the federal funds rate target range to 3.75%–4.00%, with all 12 voting members supporting the decision.
The policy statement also noted that economic activity is expanding solidly, domestic spending remains resilient, and inflation remains elevated.
Against this backdrop, the September CPI effectively tested one question: can underlying inflation continue to slow, providing a basis for the Fed to pause and observe the effects of prior tightening?
This report did not provide the expected support.
Core CPI did not decline month-over-month, and housing and non-housing services strengthened somewhat, weakening the argument that "after the September rate hike, it is possible to continue waiting."
However, one report also cannot measure the full effects of the previous rate hike, as the transmission of monetary policy to demand and prices takes time.
Benigno's judgment leans more toward further tightening.
Based on his understanding of the Fed's reaction function, policymakers consider the length of time inflation remains above target, the resilience of the economy and employment, and whether financial conditions are tight enough to restrain demand.
If the economy remains solid, the labor market does not weaken noticeably, and core services inflation remains strong, the case for further Fed rate hikes will strengthen.
Conversely, if subsequent data show a clear cooling or financial conditions tighten significantly, there is still a basis for pausing to observe.
It is also necessary to distinguish between indicators here: the Fed measures its 2% inflation target using the PCE price index, and core CPI is an important reference, so its gap from 2% cannot be mechanically converted into the number of rate hikes.
For the October 27–28 meeting, the next things to watch are producer prices, inflation expectations, employment, and financial conditions.
Among these, whether housing and non-housing services can slow again will affect the Fed's judgment on the persistence of price pressures.
The September CPI has not yet made an October rate hike a foregone conclusion, but it has raised the evidentiary threshold needed to pause rate hikes.
With core inflation failing to cool as expected, if the Fed chooses to continue waiting, it will need more convincing reasons from other data, which is another confirmation that, after the aggressive September rate hike, market disagreement over the policy path has intensified.
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