CBOE Volatility Index (VIX)
The CBOE Volatility Index (VIX) is a widely used indicator or the implied volatility of the broader US market as measured by the S&P 500 index options.
The VIX index is set to increase in value when the implied volatility of the S&P500 index options increases in value. The VIX number is often considered to be a fear gauge, acting as a fear index. Consequently, when the VIX number goes to elevated levels, it is thought that market participants are expressing added anxiety as to the US stock market (and often time US economy) as a whole.