Investing isn't easy. Even Warren Buffett councils 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, Procter & Gamble (NYSE: PG).

Procter & Gamble shares have simply crushed the S&P 500 over the last three decades:

Source: S&P Capital IQ.

Since 1980, shares returned an average of 14.1% 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 Procter & Gamble, it'd be worth $68,300.

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

Source: S&P Capital IQ.

Again, significant outperformance. Since 1995, Procter & Gamble's earnings per share have grown by an average of 8.2% a year, compared with 6% a year for the broader index. That's testament to the power of the company's brands, its global reach, and a set of smart, strategic acquisitions.

That earnings-growth dynamic has also played a role in valuations. Procter & Gamble has traded for an average of 25.2 times earnings since 1980, compared with 21.3 times for the S&P.

The company has been, without a doubt, an above-average performer historically.

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

Fool contributor Morgan Housel owns shares of Procter & Gamble. Follow him on Twitter @TMFHousel. Motley Fool newsletter services have recommended buying shares of Procter & Gamble. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.