Years ago, marijuana proponents adopted April 20 as a day to celebrate the cannabis plant, calling it "420 day." This annual celebration began long before there was a legal marijuana industry. Now, legal marijuana is a large -- and thriving -- market. You'd have to use fingers on both hands to count the number of marijuana stocks with market caps of $1 billion or more. 

There are plenty of reasons to think that the marijuana industry will continue expanding and that marijuana stock prices will move even higher. In fact, there are at least 420 million reasons why it could happen.  

Hand extended towards ocean with marijuana buds on palm

Image source: Getty Images.

A world of opportunities

Nearly all of those marijuana stocks with market caps of $1 billion or more are companies based in Canada. Several marijuana growers already supply medical marijuana for the Canadian market. And they're eagerly anticipating legalization of recreational marijuana later this year.

But many of these companies are also looking outside of Canada and even beyond North America. Here's a partial list of other countries that have active medical marijuana laws.

Country

Population 

Argentina

43.4 million

Austria

8.5 million

Australia

23.9 million

Chile

17.9 million

Colombia

48.2 million

Czech Republic

10.5 million

Germany

80.5 million

Israel

8.1 million

Italy

59.8 million

Jamaica

2.8 million

Macedonia

2.1 million

Netherlands

16.9 million

Norway

5.2 million

Slovenia

2.1 million

Switzerland

8.3 million

Turkey

78.7 million

Uruguay

3.4 million

Data source: Aurora Cannabis investor presentation. 

What's the total combined population of these countries outside of North America that allow medical marijuana? You guessed it: 420 million. 

Now for confession time. This list omitted Croatia and Romania to get to that symbolic number. Both countries also have medical cannabis laws in effect. If we added the populations of those two Eastern European countries, the total would have been 444 million. But since it's "420 day" and not "444 day," I fudged a bit.

Of course, all of the citizens of these countries won't use medical marijuana. They are all potential customers, though. And these countries certainly represent a significant market opportunity for marijuana growers.

Aurora Cannabis (NASDAQOTH:ACBFF), the company that compiled the statistics, estimates that the potential medical marijuana demand from these countries could be in the ballpark of 3 million kilograms annually. This global opportunity is important to keep in mind when thinking about the possibility of a supply glut in the Canadian marijuana market.

Thinking globally

Some of these international markets are more attractive right now than others. You can put Germany at the top of the list.

Several of the top Canadian marijuana growers already have operations in Germany. Aurora Cannabis generated more than 21% of its total revenue in the German medical cannabis market in its fiscal second quarter. In February, Canopy Growth (NYSE:CGC), the largest marijuana company in the world by market cap, reported its first quarter with at least 1 million Canadian dollars in sales from Germany.

Others have taken steps to gain a foothold in the German market. MedReleaf (NASDAQOTH:MEDFF) announced a supply agreement with Cannamedical Pharma GMBH, a leading medical cannabis distributor to pharmacies in Germany. Aphria (NASDAQOTH:APHQF) acquired Nuuvera, which gives the company a presence not only in Germany but also in several other countries. Likewise, Cronos Group (NASDAQ:CRON) has an exclusive cannabis supply agreement with Pohl-Boskamp, which distributes products to pharmacies throughout Germany.

Most of the Canadian marijuana growers targeting the German market are also working to supply other European markets. Many of the companies are looking down under to Australia as well. Aphria had supply agreements in place for Australia even before it acquired Nuuvera. Aurora Cannabis, Canopy Growth, Cronos, and MedReleaf are also in position to sell medical marijuana in Australia. 

Just the start?

The list of countries that allow medical marijuana could grow. Brazil, for example, has relaxed some restrictions on cannabis-based drugs. Should Brazil legalize medical marijuana, the country could represent a market of $1.4 billion annually, according to cannabis industry research company New Frontier Data.

But the biggest prize of all is the U.S. Although 30 states and the District of Columbia allow use of medical marijuana, federal laws in the U.S. still prohibit use and sale of the drug. However, a recent deal between Colorado senator Cory Gardner and President Trump could potentially pave the way for legislation that would change federal policies about marijuana and leave decisions on legalization to individual states.

There's no guarantee, however, that either Brazil or the U.S. will move quickly. And even in the countries that have already legalized medical marijuana, the possibility exists that the markets don't turn out to be as lucrative as marijuana growers hope they'll be. But there are more reasons on this "420 day" to think the marijuana industry has room to expand than ever before.

Keith Speights has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.