US CPI tops 4% for first time in 3 years as energy costs surge

May inflation accelerated to 4.2%, the highest since early 2023, driven by the Iran war's impact on energy prices — but a softer core reading leaves the Fed's next move uncertain.

U.S. consumer prices rose 4.2% in May from a year earlier, the fastest pace since May 2023, as the Iran war pushed energy costs higher while core inflation showed signs of moderating.

"The headline number is entirely an energy story, but the real concern is whether higher fuel costs start feeding through to the rest of the economy," said Mark Zandi, chief economist at Moody's Analytics. "It's been almost five years since we were last at the Fed's target, and that's wearing down the collective psyche."

The consumer price index climbed 0.5% from April, matching the consensus estimate and easing from the prior month's 0.6% gain. Core CPI, which strips out volatile food and energy components, rose 2.9% year over year — slightly above April's 2.8% pace but with a monthly increase of just 0.2%, below the 0.3% economists had projected. The Bureau of Labor Statistics released the data Wednesday at 8:30 a.m. in Washington.

The mixed reading creates a dilemma for the Federal Reserve. While headline inflation at 4.2% bolsters the case for tighter policy, the moderation in core prices suggests underlying price pressures may not be broadening. Fed-dated overnight index swaps currently price about 26 basis points of cumulative rate increases by year-end, little changed from before the release.

The energy component was the primary driver of the acceleration. Brent crude averaged above $90 a barrel during the survey period, reflecting supply disruptions tied to the conflict in the Middle East. Even if the war were resolved quickly, oil production capacity would take time to restore, meaning elevated energy costs could persist, according to Moody's.

The divergence between headline and core inflation is notable. Core goods prices posted a decline in May, while core services costs continued to accelerate — a split that suggests the inflation impulse remains concentrated rather than broad-based. However, the transmission chain is still unfolding: higher diesel and jet fuel costs are pushing up transportation expenses, and fertilizer market disruptions may eventually feed into grocery prices.

Real wages turn negative

One of the most concerning signals in the report was the first year-over-year decline in U.S. real wages since April 2023. Nominal wage growth is no longer keeping pace with price increases, squeezing household purchasing power at a time when three-quarters of Americans already say their incomes are falling behind inflation, according to a recent CBS News poll.

The last time the CPI exceeded 4%, in the spring of 2023, the S&P 500 fell about 3% over the following three months before recovering. Bank of America strategists led by Michael Hartnett have warned that if the CPI were to push above 5% by the midterm elections, risk assets could face significant headwinds. Historical data shows that in the past century, when CPI has breached 4%, the S&P 500 has averaged a 4% decline over the subsequent three months and a 7% decline over six months.

Policy path ahead

For the Fed, the question is whether this inflation episode is transitory or becoming entrenched. The last time the central bank faced a similar energy-driven shock — following Russia's invasion of Ukraine in 2022 — it raised rates by 75 basis points at consecutive meetings. This time, the economy is in a different position: the labor market remains resilient, but consumers are showing signs of strain.

New Fed Chairman Kevin Warsh is widely expected to hold rates steady at next week's Federal Open Market Committee meeting. But the May CPI data will likely push officials to adjust their forward guidance, formally acknowledging that the next move could be a rate increase rather than a cut. The next FOMC decision is scheduled for June 17-18.

This article is for informational purposes only and does not constitute investment advice.