U.S. stock indexes are edging lower on a relatively quiet Wall Street. The S&P 500 slipped by 0.2%, a day after setting an all-time high.

Wall Street is flirting with a record again as U.S. stock indexes drift in mixed trading. The S&P 500 rose 0.1% at the open of Tuesday's trading and is sitting

However, the S&P 500 ( ^GSPC -0.01%) 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.