U.S. consumer prices recorded their biggest increase in eight months in September as gasoline prices soared in the wake of hurricane-related production disruptions at oil refineries in the Gulf Coast area, but underlying inflation remained muted.
The Labor Department said on Friday its Consumer Price Index jumped 0.5 percent last month after advancing 0.4 percent in August. September's increase was the biggest since January and pushed up the year-on-year gain in the CPI to 2.2 percent from 1.9 percent in August.
Economists polled by Reuters had forecast the CPI surging 0.6 percent in September and accelerating 2.3 percent year-on-year. Gasoline prices surged 13.1 percent last month, accounting for 75 percent of the increase in the CPI.
The increase was the largest since June 2009 and followed a 6.3 percent advance in August. The Labor Department said Harvey was reported to have impacted refinery capacity in the Gulf Coast. It said Hurricane Irma, which struck Florida in early September, had a small impact on data collection.
Away from gasoline, price pressures were benign. Excluding the volatile food and energy components, consumer prices gained 0.1 percent in September as the increase in rental accommodation slowed and the cost of new motor vehicles and the medical care index declined. The so-called core CPI rose 0.2 percent in August.
In the 12 months through September, the core CPI increased 1.7 percent. The year-on-year core CPI has now increased by the same margin for five consecutive months.
The persistent modest readings in the core CPI are likely to worry Federal Reserve officials who have been engaged in a vigorous debate on the inflation path. Fed's preferred inflation measure, the personal consumption expenditures (PCE) price index excluding food and energy, has consistently undershot the U.S. central bank's 2 percent target for more than five years.
Fed Chair Janet Yellen has said that temporary factors such as one-off price cuts by wireless telephone companies are holding back inflation.
Minutes of the Fed's Sept. 19-20 meeting published on Wednesday showed "many participants expressed concern that the low inflation readings this year might reflect not only transitory factors, but also the influence of developments that could prove more persistent."
Last month, food prices rose 0.1 percent after a similar gain in August. The cost of rental accommodation rose 0.2 percent after surging 0.4 percent in August.
Owners' equivalent rent of primary residence rose 0.2 percent after advancing 0.3 percent in August. Prices for new motor vehicles fell 0.4 percent as manufacturers resort to deep discounting to eliminate an inventory overhang.
There were also decreases in the cost of medical care, apparel, and household furnishings. But the cost of mobile phone services rose 0.4 percent after 14 straight months of declines.