First, we can interpret this concept from the subprime mortgage crisis in the United States in 2008. "In the early 21st century, the US real estate market continued to rise, and borrowers with poor credit could also use subprime loans to obtain loans. When US house prices began to fall, a large number of subprime loans defaulted. This caused many financial institutions to see a sharp decline in capital, and Lehman Brothers went bankrupt." In fact, the liquidation of the currency circle is very similar to traditional finance. Users mortgage BGB to borrow other coins. Since the LTV is around 75%, once a large investor dumps the market and the price reaches the liquidation line, all loan orders will be liquidated, the market liquidity will be drained, and the token will flash crash and fall sharply.