It’s enough to give you a headache. Legal marijuana sales in the United States — the country that is most opposed to global legalisation of the herb — were expected to hit US$9.7 billion in 2017, according to a new report from cannabis industry analysts Arcview Market Research, in partnership with BDS Analytics.

That represents an unprecedented 33 per cent increase over 2016, shattering previous expectations about how quickly the cannabis industry could grow in the face of federal prohibition. The report further predicts the entire legal cannabis market to reach US$24.5 billion in sales — a 28 per cent annual growth rate by 2021 — as more states legalise cannabis for recreational use and existing markets mature.

“Aside from cryptocurrency, there is simply no other industry changing as rapidly or as unevenly as the cannabis sector,” Troy Dayton, Arcview’s CEO, said.

The industry’s growth is buoyed by a number of new, state-legal markets coming online in 2017. Nevada, where legal marijuana sales began in July, raked in US$27 million during the first month of sales, according to the report, prompting a supply shortage that forced the governor to issue a “statement of emergency” to bring more marijuana into the state.

Revenue for the first six months of 2017 in Colorado, Washington, and Oregon — the first three states to legalise ganja for adult use — ran 33 per cent ahead of 2016, also indicating that the market is still growing, according to the report.

In addition to the substantial economic benefits is the fact that cannabis holds the real possibility of medical treatment and relief for a wide range of conditions, and is a natural, effective and safe method to treat pain. The present opioid epidemic impacting the US is an urgent reminder that the industry needs to move forward.

Meanwhile, Australia is set to become the fourth country in the world to allow exportation of cannabis-based therapies. The federal government hopes the reforms will help Australia become a world leader in the medicinal cannabis market.

Laws to allow the exportation of Australian cannabis-based therapies will come into force in February, according to the federal health minister.

It will allow Australian-produced oils, lozenges, sprays and pills to be sold overseas for the first time. Advocates have argued the plant-based treatments can relieve severe pain associated with many medical conditions, including multiple sclerosis, and reduce the impact of cancer therapies.

Potential export markets include South America, Spain, Canada and Germany.

Australian Federal Health Minister Greg Hunt said allowing exports will help the developing domestic market to expand.

“We have a world-class reputation for our clean and green farm products. Put them all together and we are brilliantly placed to be a world leader in medical development and medical cannabis,” he said.

Officials say medicinal cannabis exports have the potential to create a lucrative, new agricultural industry within Australia, similar to that already established for the use of Australian-grown poppies for medicinal and scientific purposes.

Only Canada, the Netherlands and Uruguay have so far legalised the export of medicinal marijuana. Israel has said it intends to do so within months.