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, Marathon Oil (NYSE:MRO).

Marathon Oil shares have slightly underperformed the S&P 500 over the last quarter-century:

Mro Sp

Source: S&P Capital IQ.

Since 1987, shares have returned an average of 9% 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 Marathon Oil, it'd be worth $15,600.

Dividends accounted for a lot of those gains. Compounded since 1987, dividends have made up 83% of Marathon Oil's returns. For the S&P, dividends account for 39% of total returns.

Now, have a look at how Marathon Oil earnings compare with S&P 500 earnings:

Mro Earnings

Source: S&P Capital IQ.

Big outperformance here. Since 1995, Marathon Oil's earnings per share have grown by an average of 14% a year, compared with 6% a year growth for the broader index.

What's that meant for valuations? Marathon Oil has traded for an average of 21 times earnings since 1987 -- just 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 Marathon Oil with a four-star rating (out of five). Care to disagree? Leave your thoughts in the comment section below, or add Marathon Oil to My Watchlist

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