This article is part of our Rising Star Portfolios Series.

One of the great thrusts of modern investment theory is that the market is efficient. But decades of value investors -- greats such as Warren Buffett, Seth Klarman, and Walter Schloss -- have ferreted out pricing inefficiencies that they've then exploited for nice gains. One of the more interesting places where such inefficiencies occur is in dual-class share structures.

Dual share structures often result from a special corporate transaction or reorganization of some sort. That was the case with shares of Chipotle (NYSE: CMG), which was spun off of McDonald's with two share classes. For years, the A shares traded at a premium to the B shares, and then when the burrito roller announced that it was merging the classes, the shares met somewhere in the middle.

A few years ago, Mueller Water (NYSE: MWA) saw similar events occur. Walter Industries spun out its interest in Mueller in the form of B shares. The B shares had better voting rights -- eight times greater -- than existing A shares. Despite this, A shares at one point traded as much as 22% higher than the B class.

You'll see a similar case with my recent Rising Star buy recommendation of Grupo PRISA (NYSE: PRIS) (NYSE: PRIS-B), which you can read by clicking here. The Spanish media company recently went through a major recapitalization, which saw the original owners experience substantial dilution in exchange for a huge cash infusion.

The PRISA B shares offer nearly a $0.96 yearly dividend for the next three years or so (about an 8% annual yield) and then transform into A shares. The dividends are cumulative, too. So which would you expect to trade at a higher price? Well, they trade at approximately the same price, and sometimes the A shares even cost more than B shares. The B shares offer a better margin of safety on an already cheap stock.

If the market is efficient, why does this discrepancy exist? Or is this somehow an example of efficiency?

Interested in Grupo Prisa or have another stock to share? Join me on my discussion board and follow me on Twitter (@TMFRoyal).

This article is part of our Rising Star Portfolios series, where we give some of our most promising stock analysts cold, hard cash to manage on the Fool's behalf. We'd like you to track our performance and benefit from these real-money, real-time free stock picks. See all of our Rising Star analysts (and their portfolios) here.

Jim Royal, Ph.D., owns shares of McDonald's. Chipotle is a Motley Fool Rule Breakers selection. Chipotle and Mueller Water are Motley Fool Hidden Gems recommendations. The Fool owns shares of Chipotle and Grupo Prisa Class B stock. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.