WASHINGTON — Consumer confidence fell in May as Americans grew slightly more pessimistic about job prospects and business conditions, according to a closely followed survey.

The nonprofit Conference Board said its consumer confidence index fell to 60.8 in May — the lowest reading in six months — from a revised 66 in April. Economists polled by MarketWatch had forecast an increase to 67.5.

The decline in the index conflicts with another consumer survey by Reuters and the University of Michigan that showed an increase in May owing to a drop in gas prices.

Economists say the Conference Board index is more closely linked to the health of the U.S. labor market than the Reuters/Michigan survey, which might explain the difference.

Lynn Franco, director of consumer research at the Conference Board, said a “more pessimistic outlook” is responsible for the pullback in the index. Inflation concerns also rose.

“Consumers are considerably more apprehensive about future business and labor market conditions as well as their income prospects,” she said.

The expectations index, which measures the view of consumers in the next six months, fell to 75.2 from 83.2 last month. It’s the lowest reading since last October.

A slightly higher percentage of consumers expect business conditions to get worse during the next six months — 15.5 percent versus 14 percent in April. And 20.8 percent expect fewer jobs to be available, compared with 18.7 percent in April.

The consumer confidence index remains low by historical standards. In a healthy economy, the index averages about 95 points.

The index has more than doubled, however, since touching a record-low 25.3 in February 2009.