New York ? So much for optimism. A dramatic drop in consumer confidence sent stocks plunging Tuesday and left a key index at its lowest level of the year, heightening fears that the economic recovery is stalling.

The nation is in no mood to spend its way back to growth, but businesses have been cautiously building up inventories to prepare for increasing demand as the economy improves. Now they’re left with a question: Who’s going to buy all the cars, dishwashers and clothes heading to stores and showrooms?

The Consumer Confidence Index came in at 52.9 in June, a jarring decline from 62.7 in May, according to a survey released Tuesday by the Conference Board, a private research group. It was the biggest drop since February and came on top of several gloomy economic developments in recent days.

“We need the consumer to spend, and right now declining confidence is not the prescription for a stronger economy,” said Joel Naroff, president of Naroff Economic Advisors. “This was a bad report, no matter how you slice it.”

Generally, a reading above 90 indicates the economy is on solid footing. Above 100 signals strong growth.

The index, based on a survey mailed at random to 5,000 households, hasn’t come in above 90 since the recession began in December 2007.

Economists watch the number closely because consumer spending, which includes not just merchandise but expenses like health care, accounts for about 70 percent of U.S. economic activity and is critical to a strong recovery.

The confidence report rattled Wall Street. The Dow Jones industrial average closed down nearly 270 points, falling below 10,000 for the first time since June 10.

The Standard & Poor’s 500 index fell 33.33, or 3.1 percent, to 1,041.24, its lowest close since Oct. 5.