The report predicts increased legalisation will explode marijuana sales. AP It may seem odd that a drug that is still illegal in most parts of the world can have an annual report, but Marijuana Business Daily have produced exactly that — and all signs point to a massively growing economy.

The US cannabis industry "will pump up to $44 billion (£31 billion) annually into the country's economy by 2020, if current business and legalisation trends continue" the report says. This is more than double the $14-17 billion impact it currently has.

Ancillary revenues include licensing fees, taxes, marijuana tourism, employee spending, job creation and growth in real estate prices in a community.

Marijuana sales themselves will grow to $3.5-$4.3 billion in 2016, up more than 20% from last year, "and that's just the tip of the iceberg," the report adds.

The report estimates that "sales will climb to as much as $8 billion in 2018, when states that legalize this year will likely start coming online, and up to $11 billion in 2020."

The report adds that this drive is not just driven by medical marijuana, "sales of recreational cannabis could surpass those of medical marijuana as early as 2018, though medical marijuana revenue will continue to make up a big piece of the pie."

This chart shows the projected sales growth of marijuana in the US as well as the broader economic impact of those sales in the US:

Marijuana Business Daily

"We’re witnessing the emergence of a business that is about to become a massive economic force," claimed Chris Walsh, the managing editor of Marijuana Business Daily.

"These figures, which we deem conservative, show not only how important the industry already is to the US economy at large, but also how much more important it is about to become."

Despite such growth, knowing how to invest in a new type of economy can be difficult.

Frontier Financials Group co-founder Rick Gilchrist told CNBC that those interested should invest "in ancillary businesses that don't directly involve the marijuana plant and can operate anywhere legally."

Related businesses not "touching the plant" can include everything from growing and harvesting equipment to industrial hemp to medical containers, said CNBC.

Gilchrist also added that marketing and public relations experts willing to take on marijuana clients are especially in demand.