Wall Street was mixed with low volumes of trading Friday with major U.S. markets struggling to end in positive territory for the week. Futures for the S&P 500 were virtually unchanged before the bell,

However, the S&P 500 ( ^GSPC 0.24%) is generally considered the best barometer for the overall U.S. stock market due to its scope and diversity. Read on to see the S&P 500's average return over the last decade, and to learn what Wall Street expects in the future.

The S&P 500 was 0.2% lower in afternoon trading. The Dow Jones Industrial Average was down 169 points, or 0.4%, as of 12:47 p.m. Eastern time