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.

NEW YORK — Most U.S. stocks fell Wednesday after a report showed inflation is unexpectedly worsening for Americans . The S&P 500 dropped 0.3%, though it had been on track for a much worse loss of 1.1% at the start of trading. The Dow Jones Industrial Average sank 225 points, or 0.5%, while the Nasdaq composite edged higher by less than 0.1%.