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The key to investing is not assessing how much an industry is going to affect society, or how much it will grow, but rather determining the competitive advantage of any given company and, above all, the durability of that advantage.
-- Warren Buffett

Buffet coined and popularized the term "economic moat" when referring to a business' ability to maintain a competitive advantage over rival firms. We Fools love to find businesses that have a deep and wide economic moat, as it helps to protect the company's profits for years into the future.

We asked our team of Motley Fool contributors to share a pharma stock that they believe offers investors a wide economic moat. Read below to see if you agree with their recommendations.

George Budwell: As Pfizer (NYSE:PFE) is one of the world's largest drugmakers by total sales, has a widely recognized brand, and a ginormous sales force, it should naturally possess an abnormally large economic moat, as well. And I think this assumption is borne out by the data.

When it comes to launching a new drug, for instance, Pfizer has an uncanny ability to gobble up a disproportionate market share in record time. As an example, the drugmaker's new breast-cancer drug, Ibrance, raked in $140 million in sales during its first-full quarter on the market earlier this year. Even more impressive, this figure was nearly double what the Street was expecting in terms of second-quarter sales for the drug. In my view, Ibrance's stellar launch clearly demonstrates Pfizer's huge competitive advantage in the marketplace.

But the pharma giant's competitive advantage doesn't stop there. Despite other competing breast-cancer drugs likely to come online soon, Ibrance is projected to see sales of a monstrous $5 billion by 2020, and may one day even reach $10 billion in annual sales -- if Pfizer is successful at expanding the drug's label. Put simply, Pfizer's peers appear helpless in terms of taking market share away from Ibrance -- which is a function of not only the drug's effectiveness, but a testament to Pfizer's wide economic moat.

Brian Feroldi: Investors looking to find a business with a wide economic moat should give Johnson & Johnson (NYSE:JNJ) a serious look. The company has put up 31 consecutive years of adjusted earnings growth, and has managed to raise its dividend for 53 years in a row. You can't have that kind of track record without a strong economic moat in place.

What gives J&J's its true long-term economic advantage is its hugely diversified portfolio of businesses and products. While most of us are familiar with its consumer brands such as Aveeno, Listerine, and Zyrtec, the company generates a huge amount of its revenues from its pharmaceutical and medical device divisions. All told, the company counts 265 different operation businesses in its lineup that are working to contribute to its top and bottom lines.

J&J has also managed to diversify where its revenues comes from, as it's currently evenly split between the U.S. and international markets. This helps to further protect the company's profit stream. If one area of the world is struggling, then other regions can be depended on to help pick up the slack.

Johnson's huge size and worldwide reach give its business a tremendous moat that investors can count on year in and year out to produce solid, stable returns. For investors looking for a wide economic moat, Johnson & Johnson is a great choice.

Cheryl Swanson: Pharmas that are growth kings don't usually sport "Buffet-esque" wide moats. But here's one that does -- Allergan (NYSE:AGN). What makes this company so intriguing isn't just its rapid growth, but its dedication to maintaining a sustainable competitive advantage -- or a "wide moat," as Warren Buffet would say.   

With specialty pharma pulling back due to recent flaps over drug pricing, it makes sense to look for companies with highly defensible products, because these companies can stand the test of time. And Allergan dominates two of the most defensible specialty drug markets out there -- aesthetics and eye care. 

Botox is one critical ingredient of Allergan's wide moat. Botox not only enjoys high market share -- nearly 76% globally -- but the company uses the neurotoxin to pave the way for other less-established products, cross-selling them with Botox. And Allergan has built similar advantages in ophthalmology, where the company markets drugs for everything from dry eye to glaucoma. 

Allergan surprised Wall Street recently by selling its gigantic generic business for $30 billion in cash. The move looks brilliant, because it allowed Allergan to pull the trigger on aesthetics maker Kythera Biopharmaceuticals for $2.1 billion, and venture-backed Oculeve for dry eye. In other words, this company fully intends to defend its castle from all comers.

There are no sure bets in this market; but does Allergan look well positioned to withstand an attack from Genghis Khan and the Market Mongols, or even Attila the Hun and his sell-side analysts? You bet.