When it comes to growth, no industry is expected to pile on the green, at least from a revenue perspective, more than legal cannabis. This year alone, global weed sales are expected to grow from an estimated $12.2 billion to $16.9 billion (that's 38% for those of you keeping score at home), according to Arcview Market Research and BDS Analytics. Most of this growth will come from Canada's steady ramp-up of recreational pot sales, as well as California working out some early kinks in its adult-use market and supply chain.

Yet, despite all of the money that's already flowing into the marijuana industry, far more pot stocks are losing money than making it. This is especially true of the four most popular marijuana stocks -- Aurora Cannabis (ACB -4.35%), Canopy Growth (CGC 1.22%), Tilray (TLRY), and Cronos Group (CRON 1.24%) -- which have lost a staggering amount of money, combined, on an operating basis.

Eventually, these brand-name marijuana stocks will turn profitable, but not all at the same time. Let's take a look at which of these four is likely to lag its peers in the profit department.

A clear jar packed with cannabis buds that's sitting atop a fanned pile of twenty dollar bills.

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Profitability may be around the corner for Canada's biggest producer

Aurora Cannabis, Canada's forecasted largest producer with 700,000 kilos in peak annual output when operating at full capacity, is likely to be the first of these popular pot stocks to become profitable on an operating basis (i.e., without the aid of one-time benefits or fair-value adjustments).

In the company's second-quarter operating results press release, it was noted that positive recurring EBITDA (earnings before interest, taxes, depreciation, and amortization) was set to begin in the fiscal fourth quarter, which is between April 1 and June 30. Although positive EBITDA doesn't necessarily mean a bottom-line adjusted profit, it puts Aurora Cannabis on the presumed path to recurring profitability.

What remains to be seen is just how much of a profit investors can expect. The price that was paid to grow into the largest producer was the issuance of a lot of common stock to facilitate acquisitions. Having now issued more than 1 billion shares of stock since June 30, 2014, Aurora Cannabis has made it very difficult to generate a meaningful per-share profit. Thus, even though Aurora may be the first of these four to get into the black, its forward price-to-earnings ratio will likely still be frightening for some time to come.

Check out the latest earnings call transcripts for Tilray and other companies we cover.

A dollar sign shadow being cast atop a pile of cannabis leaves.

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Nominal profits likely await this marijuana stock, too

There's a good chance that Cronos Group won't be last across the profit finish line, either. Cronos has the advantage of only having two major production facilities -- its joint venture Cronos GrowCo and Peace Naturals -- which should help keep costs down and allow the company to focus on margin expansion via the sale of alternative cannabis products. Or, put in another context, it's a lot smaller and less complex than Aurora, Canopy, and Tilray, which means its operating expenses won't be nearly as high, providing it the ability to turn a recurring profit.

On the other hand, Cronos Group's 120,000 kilos in peak annual production is far from impressive. In fact, it may only slot the company in as the eighth-largest producer in Canada, which is on par with growers that have market caps a quarter (or less) the size of Cronos Group. This creates a scenario similar to Aurora where profitability is expected, but on a per-share basis it could be quite low, leading to a very high forward P/E ratio.

Arguably, the only thing buoying Cronos' stock right now is the $1.8 billion equity investment it received from Altria. With Cronos now cash-rich, investors believe that its stock has a high floor, or that Altria will eventually buy the remaining shares of Cronos it doesn't already own. However, the hole in this thesis is that it overlooks Cronos' subpar production and weak international expansion efforts. Even beating Canopy and Tilray to profitability, it's not a stock I'd suggest buying.

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By a hair, Tilray avoids bringing up the caboose

Although it could take until the latter half of 2020, my suspicion is that Tilray will be the third of this group to push into recurring profitability.

Following Tilray's fourth-quarter operating results and conference call commentary with analysts, it's apparent that Tilray is sort of throwing in the towel on Canada. It has close to 850,000 square feet of capacity in Canada, as well as plenty of medical marijuana patients, but CEO Brendan Kennedy sees more robust opportunities in overseas markets. This strategy shift has positive and negative implications.

On the one hand, shifting to overseas markets means focusing on medical pot patients, who tend to consume cannabis more often and are more willing to open their wallets than recreational weed users. Plus, they're more likely to use alternative products, such as oils. Alternative cannabis products have much higher margins and are far less prone to pricing pressure than dried cannabis flower. So, on a long-term scale, this is a good move for Tilray to narrow its immediate competition and focus on higher-margin consumers.

But shifting its strategy so early in the legalization process also means higher costs to establish its international infrastructure and build up its brands. This slower-than-expected ramp-up is liable to keep Tilray in the red through 2019 and into 2020.

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The dubious loser... Canopy Growth

Among the most popular pot stocks, Canopy Growth looks to be last to turn a recurring profit. Chances are that shareholders won't see this cannabis giant generating an operating profit until sometime in 2021.

Make no mistake about it, Canopy does have a number of factors working in its favor. It's likely to be the second-largest producer at more than 500,000 kilos at its peak, it has the most well-known cannabis brand in the country (Tweed), and it has a mountain of cash thanks to a $4 billion equity investment from Constellation Brands.

But this last advantage -- a boatload of cash -- is also the company's crux. With the pot industry expanding rapidly, Canopy Growth wants to deploy this capital as quickly and efficiently as possible to garner Canadian market share, get its foot in the door in the U.S. via the hemp market, and further expand into overseas markets. But doing so will cost the company a pretty penny and keep it from achieving operating profitability for at least a few more years.