Consumer confidence plunged last week to the lowest level since August as rising gasoline prices made Americans more pessimistic about the economic outlook and their finances, Bloomberg reported.

The Bloomberg Consumer Comfort Index dropped to minus 48.5 in the period that ended March 13 from minus 44.5 the prior week. Sentiment fell across most income and age groups and worsened for all education levels.

Higher gasoline prices persisted for another week, becoming a bigger concern for Americans already dealing with rising grocery bills. The report showed confidence among households with annual incomes exceeding $100,000 fell to the lowest level since November, posing a risk for consumer spending, the biggest part of the economy.

The report “shows further evidence of the mounting concerns that the U.S. consumer has about the outlook, with oil prices the main factor crimping their optimism,” said David Semmens, a U.S. economist at Standard Chartered Bank in New York. “Any weakness in the U.S. consumer creates significant concern.”