Gold, like other commodities is traded on the open market by people. Its worth whatever people are willing to pay. End of story.
IF 10,000 tons of gold was magically available tomorrow, its likely the price people would be willing to pay would significantly decrease.
There is about 170,000 tons of gold in the world currently mined. So this would be an immediate increase of about 6% in world supply. This should cause a decrease in the price, especially since this would be a huge new amount available (somewhat) immediately.
Latest Answers