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Volatility is not merely a risk measure; it is a tradable asset class in its own right. The difference between implied volatility (the market's expectation of future price movements, extracted from options prices) and realized volatility (the actual price movements that occur) creates trading opportunities. Strategies that systematically exploit this difference, known as the volatility risk premium, have been a significant source of returns for sophisticated investors.
The VIX index, often called the "fear gauge," is calculated from the implied volatilities of S&P 500 index options. It represents the market's expectation of 30-day annualized volatility. Historically, the VIX has averaged around 18-20 but has spiked above 80 during extreme crises (2008, 2020). A key empirical fact is that implied volatility is, on average, higher than subsequent realized volatility. This means that option sellers (who are short volatility) earn a positive average return, while option buyers (who are long volatility) pay a persistent premium for the protection that options provide.
Volatility mean reversion is one of the most reliable statistical properties in financial markets. When volatility spikes to extreme levels, it almost always reverts to its long-run average within a few months. This property can be exploited by selling volatility (through options or VIX derivatives) after spikes and buying volatility when it is unusually low. However, the path to mean reversion can be treacherous: volatility can continue spiking before it reverts, and short volatility positions during these periods can incur severe losses.
The term structure of volatility refers to how implied volatility varies across different option expiration dates. Normally, the term structure is upward-sloping (contango): longer-dated options have higher implied volatility than shorter-dated ones, reflecting uncertainty about the future. During market stress, the term structure can invert (backwardation): near-term options become more expensive than longer-term options as hedging demand increases. VIX futures and options allow investors to trade the slope and curvature of the volatility term structure.
Variance swaps and volatility swaps are over-the-counter derivatives that allow direct exposure to realized volatility without the directional risk embedded in options. A variance swap pays the difference between realized variance and a predetermined strike variance. These instruments isolate pure volatility exposure and are used by institutional investors to express views on future volatility levels or to hedge the volatility risk embedded in their portfolios. Understanding the distinction between variance (the square of volatility) and volatility itself is important because variance swaps are mathematically cleaner to price and hedge.