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, Public Service Enterprise (NYSE:PEG).

Public Service Enterprise shares have matched the S&P 500 over the last quarter-century:

Source: S&P Capital IQ.

Since 1987, shares have returned an average of 9.8% 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 Public Service Enterprise, it'd be worth $20,100.

Now, have a look at how Public Service Enterprise earnings compare with S&P 500 earnings:

Source: S&P Capital IQ.

Some underperformance here. Since 1995, Public Service Enterprise's earnings per share have grown by an average of 5.4% a year, compared with 6% a year growth for the broader index.

What's that meant for valuations? Public Service Enterprise has traded for an average of 13 times earnings since 1987 -- below the 24 times earnings for the broader S&P 500.

Through it all, shares have been average performers 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 Public Service Enterprise with a five-star rating (out of five). Care to disagree? Leave your thoughts in the comment section below, or add Public Service Enterprise to My Watchlist

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.