The CBOE S&P 500 Volatility Index (VIX) is known as the “Fear Index” because it is such a helpful gauge to measure how worried traders are that the S&P 500 might suddenly drop within the next 30 days.

How Does the VIX Work?

For financial instruments like stocks, volatility is a statistical measure of the degree of variation in their trading price observed over some time. On September 27, 2018, shares of Texas Instruments Inc. (TXN) and Eli Lilly & Co. (LLY) closed around similar price levels of $107.29 and $106.89 per share, respectively.

However, a look at their price movements over the past one month (September) indicates that TXN (Blue Graph) had much wider price swings compared to that of LLY (Orange Graph). TXN had higher volatility compared to LLY over the one month.