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The Greens have released the costings of their plan to legalise and tax cannabis in Australia.

The proposal also outlines the production and sale of recreational cannabis in Australia through a tightly regulated model, including establishing a new agency, the Australian Cannabis Agency, to act as the sole wholesaler between producers and retail outlets. It would also set prices and be responsible for issuing production and sales licences.

Costings from the Parliamentary Budget Office says legalising marijuana in Australia would increase the fiscal balance by $3.5 billion and increase the underlying cash balance by $3.3 billion over the Budget forward estimates period.

Taxes would lead to a surge in revenue of over $4.5 billion, with costs running at just over $1 billion.

Among other aspects of the proposal which would see sales of recreational cannabis restricted to individuals over 18 years of age, with no restrictions on the amount individuals could purchase, it assumes the average recreational cannabis consumer purchases three grams per week.

With the average joint containing approximately 0.32 grams of cannabis, that’s enough marijuana to make about 10 joints a week.

While that sounds like a lot, the plan put forward by the Greens is based on analysis of countries and states where legalisation of recreational cannabis has occurred, and acknowledges that the actual outcomes may differ significantly due to differences in policy specifications and market characteristics between Australia and overseas.

Also under the proposal, sales to overseas visitors would be permitted and individuals would be permitted to grow up to six plants for personal use.

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