Consumer confidence fell last week to the lowest level in a month, Bloomberg reported.

The Bloomberg Consumer Comfort Index dropped to a minus 44.5 in the period ending March 6, from the prior week’s minus 39.7, which was close to the highest in three years. Confidence fell the most among respondents who lacked a full-time job or any employment, and those earning less than $50,000 a year.

The index is based on responses from 250 people age 18 and over. It can range from 100, indicating every participant had a positive response to all components of the survey, or negative 100, meaning every participant had a negative response.

The drop in confidence can be attributed partly to surging gasoline prices, experts say. The added burden of higher prices may restrain the gains in consumer spending that are bolstering the economic expansion.

“Rising gasoline prices extracted a toll,” said Joseph Brusuelas, a senior economist at Bloomberg LP in New York. “Those at the lower end of the income ladder and those in the middle are being squeezed by rising costs of fuel and food, which does not bode well for discretionary spending.”

The index reflected worsening results for all three subcomponents: the measure of personal finances, Americans’ view of the economy and an index of the buying climate.