Unlike coal, gas or oil, it is relatively easy to quantify how much gold has been accrued to date. In about 1400 the world’s entire supply of mined gold would have fitted into a six-foot cube. Today, if all the coins, bars, fillings and jewellery were converted to bullion bricks, they would cover a tennis court to a depth of 35 feet, with a total value of about $6.6 trillion. About 2,700 tons of new gold are mined every year, much of it in China, the world’s largest gold-producing nation. The industry is suffering from chronic over-production even as the price of gold slips. Too many big miners are digging dirt rather than gold. Mines are shuttering.