NEW YORK — Stocks ended a disappointing January with a loss as investors questioned whether the economy will be able to sustain its big fourth-quarter growth rate. Downbeat earnings at technology companies also pulled stocks lower.

The Dow Jones industrials fell yesterday to close the month down 3.5 percent. Just 10 days earlier, the average was at a 15-month high. Investors who are increasingly uneasy about the economy, earnings and politics have been pulling money out of the market over the past week.

January was the worst month for the market since last February. Many market watchers believe January sets the tone for stocks for the rest of the year, and historical data backs that up. Since 1950, the Standard & Poor's 500's full-year direction has matched its January performance more than 90 percent of the time, according to the Stock Trader's Almanac.

But the January barometer can be faulty. Last year, when the market had its worst January ever, the Dow fell 11.4 percent for the month, and then went on to post an 18.8 percent gain for all of 2009.