Dispersion Trade (Detailed)
A Dispersion Trade is a sophisticated volatility strategy that sells options on a stock index while simultaneously buying options on the individual constituents of that index, profiting when individual stocks move more than the index as a whole — a condition known as high dispersion or low correlation.
Dispersion trading exploits the relationship between the volatility of an index and the weighted average volatility of its components. By definition, index volatility is lower than the average constituent volatility when stocks are less than perfectly correlated — the index smooths out idiosyncratic moves. A dispersion trade monetizes this relationship.
The standard dispersion trade involves selling variance (or straddles) on the index and buying variance (or straddles) on a subset of the index constituents, weighted by their index weights. The trade profits if realized correlation between stocks is lower than the implied correlation embedded in the relative pricing of index versus single-stock options — a state of high dispersion.
Implied correlation is the key input. Index implied volatility reflects both the average single-stock volatility and the assumed correlation between stocks. When implied correlation is high (investors are pricing options as though stocks will move together, as in a crisis), index options become expensive relative to single-stock options. Selling the expensive index volatility and buying the relatively cheap single-stock volatility captures this spread.
The trade profits when realized correlation turns out lower than implied correlation — individual stocks go their own ways, the index stays calmer than feared, and the short index variance position profits while the long single-stock variance positions also benefit from idiosyncratic stock moves.
Dispersion trades are also sensitive to skew differentials between the index and individual stocks. The volatility skew (the premium of downside puts over upside calls) is typically steeper on the index than on individual stocks because investors buy index puts for portfolio protection. This skew differential provides an additional edge to the dispersion seller.
In practice, dispersion trades are run by hedge funds and bank proprietary desks using sophisticated correlation models. Retail access is limited, though some exchange-traded products and structured notes offer indirect exposure to correlation trades. Understanding dispersion is valuable for any options trader because it illuminates why index options are consistently cheaper relative to single-stock options and why selling premium on indices tends to be more reliable than on individual stocks.