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 members of the S&P 500 have performed compared with the index itself.

Step on up, Schlumberger (NYSE: SLB).

Schlumberger shares have actually underperformed the S&P 500 over the last three decades:

Slbsp

Source: S&P Capital IQ.

Since 1980, shares returned an average of 8.3% a year, compared with 11.1% a year for the S&P (both include dividends). That difference adds up fast. One thousand dollars invested in the S&P in 1980 would be worth $29,400 today. In Schlumberger, it'd be worth just $13,000.

Dividends accounted for a lot of those gains. Compounded since 1980, dividends have made up about half of Schlumberger's total returns. For the S&P, dividends account for 41.5% of total returns.

And have a look at how Schlumberger's earnings compare with S&P 500 earnings:

Slbearnings

Source: S&P Capital IQ.

Not bad. Since 1995, Schlumberger's earnings per share have grown by an average of 11.9% a year, compared with 6% a year for the broader index. Schlumberger's earnings power has been strong over the years; it's just had a tough time convincing the market that earnings growth should be rewarded with share returns.

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