NEW YORK — Falling oil prices are becoming another sign of investors' deflating hopes for a speedy economic recovery.

Major stock indexes skidded 2 percent yesterday as crude fell for the fifth straight day and the Dow Jones industrial average fell to its lowest close since late April.

Lower oil prices can help the economy by reducing costs, but investors are looking to the latest slide as an unwelcome prediction that demand for energy and basic materials will remain weak as the recession lingers.