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Over the past year, a select few stocks have managed to triple their shareholders' money, including Gol Intelligent Airlines (NYSE:GOL), GW Pharmaceuticals (NASDAQ:GWPH), and Cliffs Natural Resources (NYSE:CLF). Yet just because stocks have climbed in the past doesn't mean they'll keep going, so it's important to look closely at these companies to see what prospects they still have ahead of them.

GOL Chart

GOL data by YCharts.

Gol scores

The airline industry has done extremely well lately, and the major U.S. carriers with which American investors are most familiar have produced solid gains. Yet to find the absolute best returns, you have to look well south of the border to Gol Linhas Aereas Inteligentes, which is Brazil's second-largest airline.

Gol hasn't fared as well as U.S. airlines over the past two or three years because Brazil's economy has been under siege. Tough conditions in the commodity markets hurt Brazilian growth, and that sent the country's currency dramatically lower. Yet throughout much of 2016, Gol bounced back, riding the wave of excitement over the 2016 Olympic Games and improving energy and mining markets to produce greater economic growth.

Airplane taking off.

Image source: Getty Images.

Gol has done a good job of bouncing back from extensive losses, and cost-cutting and capacity management should help the Brazilian airline take maximum advantage of improving conditions as they arise. If the Brazilian currency keeps rebounding and the economy strengthens, then Gol has a long way to go to make back all of its losses since 2014.

Investors are high on GW

GW Pharmaceuticals is up 220% over the past 12 months, and much of the interest in the company has stemmed from its exploration of treatments that it produces from marijuana. Early last year, GW announced that a study of its cannabidiol formulation Epidiolex reduced the number of monthly epileptic seizures among patients suffering from Dravet syndrome by nearly two-fifths, dramatically outpacing the study's placebo. That news sent the stock racing higher, and over the course of the year, interest in the stock has only intensified.

Looking forward, many expect GW to win Food and Drug Administration (FDA) approval for Epidiolex, but the larger concern is whether that drug will be enough to drive the stock higher from here. The company's Sativex drug for multiple sclerosis hasn't been the economic success that many had hoped for, and there are fears that pricing pressure from U.S. regulators could prevent GW from reaping as much revenue as it would like, even if Epidiolex does get approval. GW could well find further gains if its pipeline keeps expanding, but investors should expect plenty of volatility from the stock.

Cliffs rides stronger commodities higher

Finally, Cliffs Natural Resources has done the best out of these three stocks, posting a nearly 280% rise. Yet those gains were actually much higher just a month ago, and that has some investors shaking their heads about the iron-ore producer's future.

Cliffs Natural has struggled in the face of terrible conditions in the steel industry in recent years, as its iron ore goes to supply steel producers with the raw materials they need for making the metal. The bear market in commodities hit the company hard, and 2016 was a bounce-back year for Cliffs. But the biggest bump for the stock came after the presidential election, when the surprise victory of Donald Trump heralded an ushering in of new infrastructure spending that sent steel producers and their suppliers soaring.

More recently, doubts have surfaced about whether the White House will be able to move forward with its policies as quickly as investors had originally hoped. That has taken some of the wind out of Cliffs Natural's sails, and it's uncertain whether the Trump administration will be able to regain momentum and implement policies that would benefit the iron-ore producer. For those who believe that infrastructure projects will eventually gain traction, Cliffs could keep climbing in the future.

Stocks that triple are rare, and these three stocks have good stories to explain their rises. Of these three stocks, Gol seems to have the most upside potential from here, but GW Pharmaceuticals and Cliffs Natural could also rise if things go well for their respective industries.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.