In 1970, there were approximately 330,000 prisoners in the US. Today there are 2.3 million behind bars - more than any country in the history of the world. In 2009 alone there were 1.6 million drug-related arrests in the U.S. 1.3 million of these were for possession of drugs alone. Over half were related to marijuana. The forty-year war on drugs has cost $2.5 trillion.