ERBB. ArcView Market Research recently released its fourth edition of The State of Legal Marijuana Markets report, and it includes the prediction that the legal cannabis market will see a whopping $21.8 billion in total annual sales by 2020. (By comparison, at that point, the legal marijuana market could be bigger than the National Football League, which saw roughly $12 billion of revenue last year but is aiming to reach $25 billion by 2027.)