The S&P 500 is up for 8th straight week

In Friday’s trading: The stock market fizzled Friday at the end of a holiday-shortened trading day, but still logged its longest streak of weekly gains in a decade.

Investors watched for early trends in holiday sales as the busiest shopping day of the year, Black Friday, got under way. Retailers were one of two industry groups in the S&P 500 to rise.

Stocks rose for most of the day Friday, but petered out in the last half hour of trading. The New York Stock Exchange and the Nasdaq closed early, at 1 p.m. Eastern Time, and activity was lower than average a day after Thanksgiving. Thin trading can lead to sudden swings in markets.

Market results: The Standard & Poor’s 500 index ended down one point, or 0.1 percent, to 1,805.81. The Dow Jones industrial average slipped 10 points, or 0.1 percent, to 16,086.41. The Nasdaq composite rose 15 points, or 0.4 percent, to end at 4,059.89. The index has surged 34 percent this year, more than the other two indexes.

Even though the S&P 500 eased Friday, it still rose for an eighth straight week, its longest stretch of weekly advances in a decade. Winners and losers: » Wal-Mart Stores Inc., up 8 cents to $81.01. Before Black Friday even began, the world’s biggest retailer logged more than 10 million register transactions in four hours.

» Archer Daniels Midland Co., down $1.24 to $40.25. Australia rejected the conglomerate’s bid to acquire GrainCorp, saying the sale would be contrary to national interests.

A deeper look: Investors will be following retail sales trends closely to get a read on the health of retailers, as well as the wider economy. Consumer spending is a critical component of the U.S. economy.

Retail sales are expected to rise 4 percent to $602 billion during the last two months of the year, according to the National Retail Federation. But sales could come at the expense of profits, analysts expect, as retailers are likely to use more discounting to draw in customers.