2014's Biggest Stock Winners: Is There Any Gas Left in the Tank?

For many investors, the U.S. stock market's robust performance in 2014 was a welcome surprise. At the outset of 2014, Morningstar.com readers predicted a gain of just 6.5% for stocks for the year, but the S&P 500 went on to gain twice that much.

The technology, health-care, utilities, and real estate sectors led the way, with each gaining about 20% for the year. And some companies downright knocked the cover off the ball, returning 75% or, in some cases, doubling investors' money during the year.

But last year's biggest winners wouldn't necessarily make for a great shopping list, according to Morningstar's equity analysts. In fact, among the analyst-rated companies with 2014 returns of 50% or more, just one--drugmaker

Here's an overview of the rated companies that earned returns of 75% or more last year, as well as a capsule discussion of their forward-looking prospects.

2014 Return: 91.56% | Morningstar Rating: 3 Stars | Economic Moat Rating: Wide

Allergan shares nearly doubled in value in 2014, as the maker of Botox was initially pursued by hostile suitor

2014 Return: 93.70% | Morningstar Rating: 2 Stars | Moat Rating: Narrow

Shares of this medical-device maker, which specializes in heart valves, soared in 2014, owing to several positive earnings surprises. Analyst Debbie Wang notes that the firm's focus on efficiency and higher-margin products has helped plump margins, and she has assigned Edwards a narrow moat rating for its dominance in tissue heart valves. And while Wang bumped up her price target in 2014, in part because of the successful rollout of the firm's Sapien transcatheter aortic valve, the stock is still trading well above her fair value estimate of $97 a share.

2014 Return: 104.95% | Morningstar Rating: 1 Star | Moat Rating: Narrow

Video game maker Electronic Arts surprised on the upside in 2014, exceeding management's earnings guidance, thanks to growth in its mobile and online-gaming segments. And the firm's dominance of the sports genre of the video game industry earns it a narrow moat rating; EA has a nearly 50% market share within the genre. But at nearly $47 a share, Peter Wahlstrom, Morningstar's director of equity research in the global technology and media sectors, thinks the stock has gotten ahead of itself; he puts its fair value at $28.

2014 Return: 84.84% | Morningstar Rating: 1 Star | Moat Rating: None

Lower gas prices are a boon to consumers, but they also provide a tailwind to the trucking industry, which enjoyed a banner year in 2014. Knight outperformed other firms in its industry, thanks in part to its long-standing focus on efficiency and cost controls. But analyst Matthew Young says that even the best-managed firms will have trouble earning a moat in the trucking industry; it's a capital-intensive business with low switching costs and a high level of price competition. Moreover, Knight is currently trading about 50% higher than Young's fair value estimate of $19.

2014 Return: 89.49% | Morningstar Rating: 2 Stars | Moat Rating: None

The specialty and generic drugmaker industry notched tremendous gains in 2014, with the typical company in that industry gaining nearly 50%. Generic drugmaker Mallinckrodt shot out the lights. But in contrast with the branded pharmaceutical market, where margins are often lush when drugs are still on patent, companies in the generics industry compete on price, and true economic moats are difficult to come by. Analyst David Krempa asserts that Mallinckrodt, as a smaller player within the generics space, doesn't have the scale to compete with giants such as

2014 Return: 76.15% | Morningstar Rating: 2 Stars | Moat Rating: None

Cruise lines are another industry that benefits from lower energy prices, and the major cruise operators also got a boost from rebounding consumer spending in 2014. Stock analyst Jaime Katz assigns Royal Caribbean a narrow economic moat rating, noting that it and the two other major players in the cruising industry--

2014 Return: 155.81% | Morningstar Rating: 2 Stars | Moat Rating: None

Skyworks, which makes radio frequency chips used in smartphones, is benefiting from consumers' transition away from basic cellphone handsets and into smartphones. The firm generated outstanding 2014 earnings, in part because its chips are used in

2014 Return: 125.80% | Morningstar Rating: 3 Stars | Moat Rating: None

Like truckers and cruise-line operators, airlines are big beneficiaries of lower energy prices. Thus, the airline industry had a tremendous year in 2014, with the typical company gaining more than 60%. But low fuel prices could be a fleeting advantage, and at the end of the day, Morningstar deems the airline industry a no-moat business. Senior analyst Neal Dihora points out that it's extraordinarily price-competitive and customer switching costs are nil. That said, Southwest may win customer loyalty by having fewer "nuisance fees," such as charges for checked bags, and it's not the most egregiously overvalued stock on this list, even after its strong returns over the past three years.

2014 Return: 76.82% | Morningstar Rating: 2 Stars | Moat Rating: None

Like Southwest, United Continental Holdings has benefited from low fuel prices. Senior analyst Neal Dihora notes that the firm has also improved profitability by levying various fees on passengers, from baggage charges to fees for extra legroom. He points out that the firm's revenues from these fees are growing, and the fees tend to have very high margins. Yet, his overarching thesis on the industry is that fliers are exceptionally price-sensitive and barriers to entry in the airline industry are low, making it difficult for any airline to earn a moat. And while Dihora bumped up his airline price targets to account for the fact that declining energy prices will be a tailwind, United Continental is still trading above his estimate of fair value at the moment.