VIX (Volatility Index)
The VIX, formally known as the CBOE Volatility Index, measures the market's expectation of future 30-day volatility in the S&P 500, derived from the prices of S&P 500 options, and is widely used as a gauge of market fear and uncertainty.
The CBOE Volatility Index, universally known as the VIX, was introduced by the Chicago Board Options Exchange in 1993. It is computed in real time throughout the trading day using the bid-ask prices of a wide range of S&P 500 index options expiring over the next 30 days. The VIX is expressed as an annualized percentage — a VIX reading of 20 implies that options markets are pricing in an annualized price movement of approximately 20 percent in the S&P 500, which translates to a roughly 5.8 percent expected move over one month (20 divided by the square root of 12).
The VIX has earned the colloquial title 'the fear gauge' because it rises sharply during periods of market stress and uncertainty. During the 2008 financial crisis, the VIX spiked to an all-time high of approximately 89.5 in October 2008 as Lehman Brothers collapsed and the global financial system teetered on the brink. During the COVID-19 market crash of March 2020, the VIX reached approximately 85.5, briefly approaching the 2008 extreme. In calmer periods — typical of mid-cycle bull markets — the VIX often trades in the 12 to 18 range, reflecting low realized volatility and market complacency.
An important characteristic of the VIX is its strong inverse correlation with the S&P 500. When stocks fall, implied volatility typically rises as market participants rush to buy put options for portfolio protection, driving up options premiums and therefore the VIX. When stocks rally steadily, volatility subsides. This inverse relationship is so reliable that VIX futures and VIX-related exchange-traded products were created to allow investors to hedge equity portfolios or express views on future volatility. Products like VXX (iPath S&P 500 VIX Short-Term Futures ETN) provide leveraged exposure to VIX futures.
The VIX is also useful as a measure of market complacency. Extended periods of very low VIX readings — particularly sustained readings below 13 — have historically preceded significant volatility spikes, as compressed volatility regimes can unwind dramatically. This pattern, sometimes described as the 'volatility cycle,' reflects that long stretches of low volatility encourage risk-taking and leverage-building, which ultimately creates the conditions for the next sharp spike.
For practical market analysis, many participants watch a few key VIX thresholds: readings below 15 are generally considered low volatility and complacent; 15-25 is the normal range; 25-35 indicates heightened uncertainty; and readings above 35 have historically corresponded to severe market dislocations. The CBOE also calculates derivative VIX products for individual sector indices and international markets, expanding the toolkit of volatility analysis beyond the core S&P 500 measure.