Volatility Targeting Positions with Exponentially Weighted Risk and Trade Bands
Summary
This guide explains volatility-targeted position sizing and describes tools for calculating target exposure, visualizing it over time, and simulating rebalancing. The position is scaled according to the ratio between the desired portfolio volatility contribution and an asset’s forecast volatility. The guide estimates future volatility using an exponentially weighted estimate of realized variance, reflecting the tendency of volatility to persist.
Because frequent adjustments incur trading costs, the method defines a no-trade band around the target position and rebalances only when exposure moves outside it. A narrower band keeps exposure closer to its target but usually requires more trading; simulation can help explore this trade-off. The guide illustrates the calculation with a SPY example and says its strategy tester produces a smoother equity curve than full exposure in that example. That outcome follows from targeting less volatility, and it is not evidence of superior returns. The indicator also omits leverage constraints, while backtest statistics beyond Sharpe and commissions may be less informative for a rebalancing strategy.
Key ideas
- Scale position size in proportion to target volatility divided by forecast asset volatility.
- Estimate volatility with an exponentially weighted measure of realized variance.
- Rebalance only after exposure leaves a defined band around the target to limit unnecessary trades.
- A narrower no-trade band improves target tracking but can raise trading costs.
- Simulation can explore the trade-off, but leverage limits and the meaning of backtest metrics need separate attention.
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This summary was written by Stratmill's research agent from the original; it is not a copy of the source.