A few big winners keep U.S. stock market afloat in 2015

(Reuters) - Amazon's stock price surge into Friday made it the latest of a series of companies to boom following results, and its performance this year, along with a few others, has basically kept the S&P 500 above water.

Data from S&P Dow Jones Indices shows that the gains in Amazon (AMZN.O), Facebook (FB.O), Google (GOOGL.O) and Netflix (NFLX.O) account for more than 50 percent of the broad S&P 500's rise of just over 1 percent so far in 2015. Add in Apple (AAPL.O), and those five companies account for nearly 60 percent of the year's gains, according to S&P index analyst Howard Silverblatt.

Internal measures show fewer stocks are driving the market's gains, something that has happened in the past when equities were nearing a peak. The year so far has been bifurcated between big winners and big losers, with 35 stocks in the S&P up at least 25 percent this year, and 28 down that much.

"It's not a matter of a rising tide lifting all boats," said Silverblatt. "It's every boat for themselves."

(Reporting by David Gaffen, Rodrigo Campos and Christine Chan; Editing by David Gregorio)