For years, finance academics scoffed at the notion of investment skill, preferring to adopt the efficient market hypothesis (EMH). According to EMH, stock picking is a waste of time, because a security's price reflects all relevant information at any given moment. In this framework, consistently beating the market is an anomaly attributed to a string of luck that's bound to happen with enough participants.

A recent paper, however, undermines that theory. The authors used the quantitative tools of finance academics to show that Warren Buffett's investing record, perhaps the greatest "anomaly" of all (and a real thorn in the theoreticians' side), can't be explained by luck or risk. Instead, it's the product of skill.

"I'd be a bum ...
... on the street with a tin cup if the markets were always efficient," Warren Buffett told Fortune magazine in 1995. So while Buffett would agree that the market is mostly efficient, that still leaves him room to earn his keep.

He does this by taking action only when a great business becomes temporarily undervalued. The distinction between "mostly efficient" and "always efficient" makes all the difference in the world.

Hitting the 99.99th percentile
Buffett is the best-known practitioner of value investing, the strategy pioneered by his mentor Benjamin Graham, and his track record is a wonderful illustration of value investing's efficacy over time. Between 1976 and 2006, Berkshire Hathaway's stock portfolio beat the market in 28 out of 31 years -- consistency that puts it in the 99.99th percentile. Yet this combination of consistency and Buffett's margin of outperformance -- 14.65 points per year over the S&P 500! -- led the authors of the aforementioned study to conclude that neither risk nor luck can explain these extraordinary numbers.

Usefully, the paper also debunks the myth that value investing means systematically buying low price-to-earnings or low price-to-book value stocks. In analyzing Berkshire Hathaway's stock holdings, the authors found that they are best characterized as large-cap growth. The Berkshire portfolio contains companies with consistent growth profiles that span decades, such as American Express (NYSE: AXP) and ConocoPhillips (NYSE: COP).

To invest like Warren Buffett, look for large companies with high returns on capital (an indication that they have a competitive advantage) and low debt at a reasonable price. When I screened for these criteria, I found stocks like these:

Return on Equity

Return on Capital

Market Capitalization (Billions)

Adobe Systems (Nasdaq: ADBE)




Cisco Systems (Nasdaq: CSCO)








NYMEX Holdings (NYSE: NMX)








One of the stocks on this list -- Pfizer -- happens to be a current Motley Fool Inside Value recommendation. It lends weight to the screen, but the converse isn't true. After all, showing up on a screen would be no more than the first step in a long vetting process before a stock became a recommendation. (I know, because I work on this newsletter.)

It's simple, but it isn't easy
With stock market volatility at or near a multiyear high, some outstanding companies are currently on sale. That doesn't happen very often, and investors who stick to the following principles stand to profit:

  1. Stocks are fractional ownership interests in businesses.
  2. Businesses have a value.
  3. The value of entrenched, predictable businesses can be estimated with reasonable confidence.
  4. Purchasing a stock at a price below the business's true value will produce superior returns.

Of all the investing strategies I understand, this is the only one I find practical. Still, it requires a combination of knowledge, hard work, and hard thinking -- no easy task to carry out. At Inside Value, that's what we do all day long.

If those principles make sense to you, too, click here to join us free for 30 days. There is no obligation to purchase, and you can find out more about value investing and see our latest picks.

This article was first published Jan. 11, 2008. It has been updated.

Alex Dumortier has no beneficial interest in any of the companies mentioned in this article. Pfizer, American Express, and Berkshire Hathaway are Inside Value recommendations. FedEx and Berkshire are Stock Advisor picks. The Motley Fool also owns shares of Berkshire Hathaway and fully discloses all such interests.