US inflation spiked again in June, jumping 5.4% over the past 12 months for its biggest gain since August 2008, according to official data released today.

Compared to May alone, the Consumer Price Index (CPI) surged 0.9%, seasonally adjusted, with over one-third of that rise driven by a 10.5% gain in used car prices, the Labor Department reported.

The vaccine-fueled reopening of the US economy has caused inflation to accelerate.

This is due to supply bottlenecks as well as dynamics like rental car companies' struggles to rebuild their fleets and a global shortage of semiconductors that's hampered auto production.

US energy prices have also rebounded after sinking in the midst of the pandemic shutdowns, with gasoline surging 45.1% over the past year, unadjusted, and 2.5% in the month, the report said.

Food prices rose a more modest 2.4% for the year and 0.9% in the month.

But even excluding the more volatile food and energy prices, "core" CPI over the 12 months to June jumped 4.5% - unadjusted - the biggest increase since November 1991, the Labor Department said.

Ahead of the report, economists said they expected inflation to start trending down in coming months, but noted that price pressures persist.

The "price gains were widespread as unleashed pent-up demand outstrips diminished supply," said Kathy Bostjancic of Oxford Economics.

"We believe this will be the peak in the annual rate of inflation," she said in an analysis, but "price increases stemming from the reopening of the economy and ongoing supply chain bottlenecks will keep the rate of inflation elevated."