Volatility Index (VIX), also known as panic index, has become an excellent market sentiment tracking indicator and risk hedging tool because it effectively reflects the panic and risk aversion of American stock market.

It is the index officially launched by CBOE in 1993. It is first used to measure the market's expectation of the fluctuation in the next 30 days implied by the flat option of S&P 100 index. The higher the index point, the greater investors' expectations of market fluctuations, which usually corresponds to the panic of the stock market crash, so it is also called the fear index.