The drops in the US stock market could cut overall spending by $140 billion, or 1.3 percent, over the coming year, says Paul Dales, senior US economist at Capital Economics.
Dales forecasts that the stock market turmoil could reduce the US economy's annual growth rate by half a percentage point through 2012.
There isn't much to spare.
In the first half of the year, the economy grew at a scant 0.8 percent annual rate.
That helps explain the dive on Wall Street: Stocks are falling partly on fears that the nation could slip back into a recession.
Tumbling stock prices could especially depress spending by wealthier consumers.
Eighty percent of stocks belong to the richest 10 percent of Americans. And the richest 20 percent represent about 40 percent of consumer spending.
Luxury retailers that have helped sustain the economy could suffer.
Image: A trader reacts at the S&P 500 Futures pit in Chicago on Monday.