Speculators' manipulation of gold futures market. More and more evidences show that the gold plunge on April 20 13 12 was caused by speculators' manipulation in the gold futures market. It is reported that since the beginning of 20 13, Credit Suisse, Societe Generale and Goldman Sachs have all publicly stated that the gold bull market has ended. Generally speaking, the gold in the world is in ounces. In ancient China, gold was measured in ounces. It is a very important metal, not only a special currency for reserve and investment, but also an important material for jewelry industry, electronics industry, modern communication, aerospace industry and other departments.