The largest monthly jump in gas prices in six decades caused a sharp spike in inflation in March, creating major challenges for the inflation-fighters at the Federal Reserve and heightening the political challenges of rising costs for the White House.

U.S. inflation was unchanged in July as rising prices for some imported goods were balanced by falling gas and grocery prices, leaving overall prices modestly higher than a year ago.

The Labor Department has cut back on the inflation data it collects because of the Trump administration’s government hiring freeze, raising concerns among economists about the quality of the inflation figures just as they are being closely watched for the impact of tariffs.

Inflation in the United States dropped last month to its lowest point since it first began surging more than three years ago, adding to a spate of encouraging economic news in the closing weeks of the presidential race.