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, American Electric Power (NYSE: AEP).                     

American Electric Power shares have underperformed the S&P 500 over the past quarter-century:

Aep

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). That difference adds up fast. One thousand dollars invested in the S&P in 1987 would be worth $19,200 today. In American Electric Power, it'd be worth $10,900.

Dividends accounted for a lot of those gains. Compounded since 1987, dividends have made up about 90% of American Electric Power's total returns. For the S&P, dividends account for 39% of total returns.

Now have a look at how American Electric Power earnings compare with S&P 500 earnings:

Aep

Source: S&P Capital IQ.

Pretty heavy underperformance here. Since 1995, American Electric Power earnings per share have increased by an average of 1.5% a year, compared with 6% a year for the broader index. 

What's that meant for valuations? American Electric Power has traded for an average of 15 times earnings since 1987 -- below the 24 times earnings of the broader S&P 500.

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

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