Wall Street is hanging near its record on Friday after big companies turned in a mixed set of profit results. The S&P 500 was edging down by 0.1% in early trading, a day after pulling away from its all-time high following a weaker-than-expected profit forecast from Walmart.

Wall Street is retreating from its record as a slide for Walmart weighs on U.S. stock indexes Thursday. The S&P 500 was down 0.6% in morning trading after setting all-time highs in each of the last two days.

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.