Planet Money says they are estimated to be worth $4T total [1] [1] http://www.npr.org/sections/money/2016/02/03/465476188/episode-681-the-oil-kingdom http://ww

Planet Money says they are estimated to be worth $4T total [1] [1] http://www.npr.org/sections/money/2016/02/03/465476188/episode-681-the-oil-kingdom http://www.npr.org/sections/money/2016/02/03/465476188/episo...