Investing isn't easy. Even Warren Buffett counsels that most investors should invest in a low-cost index like the S&P 500. That way, "you'll be buying into a wonderful industry, which in effect is all of American industry," he says.

But there are, of course, companies whose long-term fortunes differ substantially from the index. In this series, we look at how individual stocks have performed against the broad S&P 500.

Step on up, Harsco (NYSE:HSC).

Harsco shares have underperformed the S&P 500 over the last quarter-century, driven by a big fall since 2006:

Source: S&P Capital IQ.

Since 1987, shares have returned an average of 7.8% a year, compared with 9.7% a year for the S&P (both include dividends). One thousand dollars invested in the S&P in 1987 would be worth $19,200 today. In Harsco, it'd be worth $11,100.

Dividends accounted for a lot of those gains. Compounded since 1987, dividends have made up 61% all of Harsco's returns. For the S&P, dividends account for 39% of total returns.

Now have a look at how Harsco earnings compare with S&P 500 earnings:

Source: S&P Capital IQ.

Underperformance here, too. Since 1995, Harsco's earnings per share have increased by an average of 2% a year, compared with 6% a year for the broader index.

What's that meant for valuations? Harsco has traded for an average of 18 times earnings since 1987 -- below the 24 times earnings for the broader S&P 500.

Through it all, shares have been slight disappointments over the last quarter-century.

Of course, the important question is whether that will continue. That's where you come in. Our CAPS community currently ranks Harsco with a three-star rating (out of five). Care to disagree? Leave your thoughts in the comment section below, or add Harsco to My Watchlist