The Quant Quake Hit Strategies That Should Not Have Been Correlated
In August 2007 quantitative equity funds suffered sharp simultaneous losses over a few days, then largely recovered. The episode revealed crowding nobody could see.
What Happened
Over several days in August 2007, quantitative equity hedge funds experienced severe losses. Strategies that had performed consistently for years lost substantial amounts in a compressed period, and many then recovered a significant portion within weeks.
The peculiar feature was that funds using proprietary, independently developed models experienced remarkably similar losses at the same time.
The Crowding Problem
Quantitative equity strategies typically identify securities that appear cheap or expensive on measurable characteristics: valuation, momentum, quality, and similar factors. Models are built independently and treated as proprietary.
The difficulty is that different teams analysing the same data with similar academic foundations tend to reach similar conclusions. Independently developed models converge on overlapping positions.
Every fund believed it held a proprietary portfolio. Collectively they held approximately the same portfolio, and none could observe that.
The Unwind Mechanism
The generally accepted explanation is that one or more large participants began liquidating, possibly to raise cash for losses elsewhere as credit markets deteriorated that summer.
Selling positions held widely by similar funds pushed those prices adversely. Other funds, seeing losses and risk limits breaching, reduced their own positions, which were the same positions. Each reduction worsened the losses of everyone still holding.
The recovery afterward is what confirms the diagnosis. The positions had not become fundamentally wrong. They had been sold by people who needed to sell, and prices returned once the forced selling stopped.
Why Leverage Made It Severe
These strategies typically generate small returns per position and use substantial leverage to produce attractive overall returns.
Leverage means modest adverse moves trigger risk limits and margin requirements, forcing reduction. That converts a price move into forced selling, which is the mechanism that turns a crowded trade into a cascade.
What It Taught
The practical response involved attention to crowding as a distinct risk. Funds began monitoring how similar their positions were to those of comparable strategies, using measures of factor exposure and estimates of how many days it would take to exit given normal trading volumes.
That last measure, days to liquidate, is the most useful single addition. A position that requires ten days to exit is a fundamentally different risk from one requiring an hour, regardless of what a volatility based model reports.
The episode also served as an early signal of the broader crisis. Forced selling in equity strategies reflected stress originating in credit markets, and the transmission across apparently unrelated asset classes was a preview of what followed in 2008.
The Bottom Line
Independently built models converged on the same portfolio, and one seller's liquidation became everyone's loss. Measure how crowded a position is and how long it takes to leave, because volatility models will not tell you either.