What August CPI Data Tells Us About the Fed's Next Move

Core CPI came in at 0.3% month-over-month in August, above the 0.2% consensus estimate. That's the number that moved rate hike probabilities from "likely" to "near certainty" for the Fed's September meeting. The annual core read is 2.4%, still above the Fed's 2% target, and the headline number jumped 0.4% from July on the back of energy prices pushing higher.

This is the last major inflation print before the September 15-16 FOMC meeting, which means it's basically the tiebreaker. Fed officials had been saying the decision could go either way depending on what the August data showed. Now we know.

Energy is the obvious driver. Oil pushed above $100/barrel this week as the Middle East and Russia-Ukraine wars keep supply tight, and U.S. retail diesel hit a record. Energy prices rose 2.1% in August alone. Gasoline, diesel, and jet fuel all moved higher, and that kind of move tends to bleed into other categories over time through transportation and production costs.

But it's not just energy. Services ex-energy and rent climbed 0.5%, led by a record jump in wireless telephone service prices. Hotel rates and airline fares also posted strong gains. Used and new vehicle prices ticked up. And there's an interesting data point buried in the report that connects to the AI buildout: computer software and accessories prices rose 25.4% year-over-year, a record, while computer hardware and smart home devices were up 8.4%. That's the data centre boom showing up in the inflation numbers.

Grocery prices were flat, and owners' equivalent rent (the biggest piece of CPI) only rose 0.2%, so shelter isn't accelerating. But the breadth of the report is what matters. It's not one category spiking and pulling everything up. It's broad-based pressure across goods and services.

Chairman Kevin Warsh said last month the Fed would "have work to do" if it couldn't "be confident that underlying inflation is moving to our objective, clearly and at sufficient speed." This report doesn't give him that confidence. Core CPI at 0.3% monthly translates to a 3.6% annualized run rate, well above target. The year-over-year read is decelerating, but slowly.

The Fed's preferred measure is PCE (personal consumption expenditures), not CPI, and that report drops at the end of the month. But economists are already penciling in a 0.3% core PCE print for August based on Friday's CPI data. That keeps the Fed on track to hike.

Rate futures moved immediately after the release. The market is now pricing a 25 basis point hike next week as almost guaranteed, with high odds of a second increase before year-end. That's a shift from earlier in the week when some participants were still betting on a hold.

Here's the part that complicates the picture. Real average hourly earnings fell 0.3% year-over-year in August. That's wages adjusted for inflation, and it's been negative since the Iran war started pushing energy prices higher. So Americans are dealing with higher prices and stagnant purchasing power at the same time.

The Fed's job is to cool demand by raising borrowing costs, but demand isn't the only thing driving inflation right now. Supply shocks from geopolitical conflicts and the semiconductor/AI infrastructure buildout are pulling prices higher independent of consumer spending. Raising rates doesn't fix an oil supply problem or magically create more data centre capacity. It just makes everything more expensive to finance.

That's the bind. If inflation expectations start moving higher because people see energy prices climbing and assume everything else will follow, the Fed has to act. But if the inflation is driven by supply constraints that rate hikes can't solve, tightening policy just slows the economy without addressing the root cause.

The September FOMC meeting is next week. A 25bp hike is the baseline now. The question is whether the Fed signals this is the start of a hiking cycle or a one-and-done move to keep inflation psychology in check.

Watch the dot plot (the Fed's rate projections) and the post-meeting press conference. If Warsh talks about "ongoing pressures" and "additional tightening likely," that's a hawkish tilt. If he frames it as "recalibrating policy" or "addressing near-term risks," that leaves the door open to pause after September.

The PCE report at the end of the month will matter for the November decision. If core PCE comes in at 0.2% instead of 0.3%, that gives the doves on the committee ammunition to argue for a pause. If it matches or exceeds 0.3%, the case for a second hike gets stronger.

Energy prices are the wildcard. Oil above $100 changes the inflation math fast. If crude stays elevated or pushes higher, the Fed's going to keep tightening regardless of what the rest of the data says. If there's a ceasefire or supply relief and oil pulls back to $85-90, that takes pressure off the whole picture.

One thing to keep in mind: some of these moves are volatile and mean-revert. Wireless service prices jumping 25% in a month is probably a one-time pricing adjustment that won't repeat. Airline fares and hotel rates swing with seasonality and demand patterns. Computer equipment prices are tied to chip shortages and AI demand, which could ease as supply catches up.

The Fed knows this. They're not going to overreact to a single month of noisy data. But they also can't ignore a trend. Core CPI has been running at or above 0.3% for three consecutive months now. That's persistent, not transitory.

Stephen Juneau at Bank of America said it well: "It's not really a report that makes us get more concerned about the inflation outlook," but it's enough to force the Fed's hand on a September hike. The doves on the FOMC probably wanted to see 0.2% or lower to justify holding rates steady. They didn't get it.

This is a setup where the macro data is forcing the Fed into a defensive position. They're not hiking because the economy is overheating. They're hiking because inflation is sticky and energy shocks keep pushing the numbers higher. That's a different dynamic than a typical tightening cycle.

For traders, the playbook is straightforward: watch how risk assets react to the first hike, monitor the pace of any follow-up moves, and pay attention to whether the Fed's tightening actually slows demand or just creates volatility. Rate hikes historically pressure equities, especially growth stocks with long-duration cash flows, but the response isn't automatic. It depends on whether the market thinks the Fed can engineer a soft landing or if this turns into a hard stop.

The August CPI report didn't change the fundamental picture. It just clarified what the Fed's next move will be. What happens after that depends on whether inflation starts moving back toward 2% on its own or whether the Fed has to keep tightening until something breaks.