When a transaction involving marijuana is made, both the buyer and sellers are innately better off. This is because a voluntary exchange, in any case, infers that the buyer would rather have the product than the money, and that the seller would rather have the money than the product. Prohibition was meant to be the end of voluntary exchanges involving marijuana. But, historical evidence shows that, "a prohibition of drugs, alcohol, gambling, prostitution, and other commodities demonstrates that a sizeable fraction of the population continues to supply and demand commodities that are prohibited" (Miron). So, not surprisingly, prohibition of marijuana has done very little, if anything, to cease the supply and demand of marijuana. In fact, rather than stopping supply and demand, prohibition has only succeeded in driving it underground, creating a black market. Prohibition can even increases demand simply through the "forbidden fruit effect", in which something being illegal makes it more enticing. Even after the almost one million arrests made annually from marijuana, there is a score of more users for each of the former, showing that prohibition has left demand virtually undeterred. You would have to assume that prohibition decreases supply at least to some extent. There are people whose job it is to keep marijuana out of the U.S., it is illegal to grow marijuana in the U.S., and the costs of manufacturing, transporting and distributing marijuana are increased because it all must be done in secret. But, "black market suppliers face low marginal costs of evading tax laws and regulatory policies, and this gives them a cost - advantage relative to legal suppliers" (Miron). This means that the increased costs of factors of production are cancelled out by increased profits, once again nullifying the effects of prohibition. When it comes down to it, prohibition will never carry enough clout to take on supply and demand.