Look-Ahead Bias in Volatility Backtests - Why Most VRP Percentiles Silently Cheat (and How to Fix It)

The article discusses the importance of avoiding look-ahead bias in options backtesting, particularly when working with historical data for features like volatility risk premium (VRP) percentiles. Look-ahead bias occurs when future information is used to make decisions about past events, leading to overly optimistic performance metrics that do not reflect real-world trading conditions.

Key Points:

1. Look-Ahead Bias in Percentile Calculations:

   • When calculating VRP percentiles for a given date, using the entire historical dataset can introduce look-ahead bias because early data points will be compared against future information.
   • This biased percentile calculation can lead to incorrect conclusions about when volatility risk premium was high or low.

2. FlashAlpha's Historical API:

   • FlashAlpha provides a historical options analytics API that ensures percentiles are calculated correctly by only using past data up to the current date, thus avoiding look-ahead bias.
   • This feature is crucial for accurately backtesting strategies based on VRP percentiles without statistical artifacts.

3. Other Common Sources of Look-Ahead Bias:

   • Rolling z-scores with expanding window means and standard deviations.
   • Regime labels derived from thresholds on historical distributions.
   • Volatility-of-volatility

Read the full article at DEV Community

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