rijuana to a memeber of the club in a cannabis club on August 22, 2014 in Barcelona, Spain. Under Spanish law marijuana can be consumed and grown for personal use. According to self-regulated Cannabis Associations of Catalonia (FEDCAC) and Cannabis Associations Federation of Catalonia (CATFAC) there are currently more than 650 cannabis clubs in Spain, 55 of which are regulated under the Code of Good Practice by these associations. The clubs are for members only, who have to be Spanish residents over 21 years of age, and who are introduced to the club by an existing member. More than half of the cannabis clubs can be found in Barcelona, where authorities are have imposed a one-year moratorium on new licenses for cannabis associations and it is searching for new ways to regulate these clubs as they are becoming increasingly popular. David Ramos/Getty Legal weed in North America is expected to reach $22.6 billion in revenue in 2021. But many won't be spending their money on marijuana the way they do today.

Recreational cannabis spending is expected to outpace medical marijuana sales for the first time in 2019, according to a comprehensive new report from Arcview Market Research.

It means new users will likely flood the recreational market in the next few years, with some switching over from medical marijuana programs in their states. California and Canada, which could legalize marijuana outright as early as July 1, 2018, are projected to drive major growth because of their population sizes.

A majority of Americans live in states that have access to the drug for medical use. But as the recreational market ramps up, some users could see a change in the way they buy bud.

Tom Adams, editor in chief of Arcview Market Research, says for medical marijuana patients in states that have since legalized marijuana outright, "their lives have not changed much."

"They go into the same stores — or even nicer or bigger stores, now that there are a lot more of them — and they just shop at the medical cash register," Adams says.

(Dispensaries often times have a counter for recreational sales and a counter for medical sales, or the retail shops specialize in one market. Washington folded its medical market in 2015.)

The biggest difference in how medical and non-medical users pay for pot might be taxation.

According to Adams, people who buy marijuana for recreational use in Colorado can expect to pay between 15% and 20% more than medical patients do. The state places a 2.9% sales tax (plus local taxes) on both varieties of marijuana, but it waives the 10% state marijuana tax for patients. Many dispensaries there also offer steep discounts for medical buyers.

When California rolls outs its recreational market in 2018, the state will impose a 15% tax on sales of the drug, but only non-medical users will have to pay it.

A member of staff fills a box with marijuana buds named 'Old School' in a Ccannabis club on August 22, 2014 in Barcelona, Spain. Under Spanish law marijuana can be consumed and grown for personal use. According to self-regulated Cannabis Associations of Catalonia (FEDCAC) and Cannabis Associations Federation of Catalonia (CATFAC) there are currently more than 650 cannabis clubs in Spain, 55 of which are regulated under the Code of Good Practice by these associations. The clubs are for members only, who have to be Spanish residents over 21 years of age, and who are introduced to the club by an existing member. More than half of the cannabis clubs can be found in Barcelona, where authorities are have imposed a one-year moratorium on new licenses for cannabis associations and it is searching for new ways to regulate these clubs as they are becoming increasingly popular. David Ramos/Getty

It's potentially more expensive, but recreational weed has fewer logistical challenges for users.

In states where medical marijuana is legal, patients get a letter of recommendation from their doctor to use and carry small amounts of the drug. Eligibility varies dramatically by state. In New Jersey, patients may qualify if they suffer from a debilitating or life-threatening disease, such as cancer, epilepsy, or multiple sclerosis. Meanwhile, Californians can get a recommendation via an app. Their medicine is sold in retailers registered with the state.

There are limitations on the quantity and form of drugs purchased in some states. New York and Minnesota have two of the strictest medical marijuana programs in the nation, and allow patients to buy a 30-day supply of "non-smokable" marijuana, such as gel capsules or oils.

By comparison, the recreational marijuana market seems much more lax.

In Colorado, where there are more dispensaries than Starbucks and McDonald's locations combined, residents and tourists alike can buy up to one ounce of weed. They need only present a valid ID that shows they're over 21. The same is true in Washington, which also legalized marijuana outright in 2012. Both states topped $1 billion in legal cannabis sales last year.

According to Arcview, the recreational market will overtake medical in revenue in 2019. The gap will continue to widen as (presumably) more recreational markets come online.

Adams said the data was not all that surprising.

"There's huge growth in the user base when you stop requiring people to get medical recommendations ... when you have stores selling edibles and concentrates, and not just the dealer around the corner selling bags of weed," Adams says.