WASHINGTON — Confidence in the economy eroded this month as Americans became more worried about the job market.

A business research group said Tuesday that its consumer confidence index fell to 90.4 in November, down from 99.1 in October. The index is at its lowest level since September 2014.

The share of Americans surveyed by the Conference Board anticipating more jobs in the coming months fell. Fewer people also expect to see their incomes increase. The percentage describing jobs as “plentiful” declined to 19.9 percent from 22.7 percent.

The decline in the confidence index comes after a robust month of hiring in October. Employers added 271,000 jobs last month as the unemployment rate settled at a healthy 5 percent, an indication that companies see the economy as continuing its gradual, six-year expansion from the depths of the recession.

The drop in consumer confidence was a curveball for many economists, some of whom warned that the population might be reflecting concerns about hiring momentum while others could not reconcile the survey with other indicators hinting at a resilient U.S. economy.

“November’s results could be sending a cautionary signal about the key economic variable of job growth,” said Joshua Shapiro, chief U.S. economist at the consultancy MFR.

The economy has strengthened by many measures over the past month. Hiring averaged just 145,000 in September and August, as the weight of China’s slowing economy has damaged growth prospects worldwide, the dollar has risen in value and oil prices remain low amid relatively weak demand.

U.S. economic growth appears to have improved slightly after slowing in the July-September quarter.