January 1st was an important date for the North American marijuana industry with the drug becoming legal in California. Shares in cannabis-related companies across the state increased sharply since the start of the year, adding almost $2 billion in value. California is by far the largest state (it's the world's sixth largest economy) to legalize pot and that is going to have a noticeable impact on the industry over the coming decade. The grass is going to get very green indeed.The Cannabis Industry 2017 Annual Report has revealed that sales of medical and recreational marijuana are going to start taking off in 2018. Sales of medical and recreational marijuana are going to reach $4.75 and $6 billion this year respectively. By 2023, both forms of the drug will be higher than $20 billion before hitting $24 billion in 2025.