Turk and Blumen discuss how gold is not just another commodity, because -- in contrast to the likes of oil, corn and copper -- the total aboveground stock of gold is being added to all the time. Gold is not used up or destroyed. This is why annual mine supply (at just 1.8% of total aboveground gold) exerts so little influence on the gold price. James Turk argues that gold should not be considered as an "investment", as it does not generate a cash flow. Both men differ slightly on the question of whether or not gold can be considered money."