NEW YORK (CNNMoney.com) - Stocks slumped Friday morning, the last trading session of the year, as investors kept an eye on the yield curve and cashed out of a number of recent market winners.

The Dow Jones industrial average (Charts), the S&P 500 (Charts) index and the Nasdaq composite (Charts) all retreated in the early going.

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Equities slipped Thursday in a late-day selloff, with investors consolidating at the end of a choppy year. That consolidation continued Friday morning.

Stock declines were broad based, with 28 out of 30 Dow issues falling at the open Friday.

Oil service stocks -- among the best performers of 2005 -- were hit hard at the open, as were a variety of technology stocks.

Barring a stupendous Friday rally, the major gauges are set to end the year with middling gains.

As of Thursday's close, the Dow is flat for 2005, the Nasdaq is up 2 percent, the S&P 500 is up 3.5 percent and the Russell 2000 is up 4.1 percent.

U.S. light crude oil for February delivery fell 43 cents to $59.89 a barrel in electronic trading, giving some support to stocks in the early going.

But countering that was another inversion of the yield curve. For the fourth day in a row, the 10-year note yield dipped below that of the two-year -- an aberration that could signal an economic slowdown. (For more, click here.)

Treasury prices gained Friday morning, lowering the yield on the 10-year note to 4.34 percent from about 4.36 percent late Thursday. Bond prices and yields move in opposite directions.

The dollar rallied versus the euro and was little changed versus the yen.

COMEX gold for February delivery fell $1.80 to $515.70 an ounce.

In global trade, major Asian markets ended lower, while European shares fell at midday.