Why Adjusted Stock Prices Can Differ Across Backtesting Platforms

Summary

A user reports a discrepancy between a trade’s recorded execution price and the stock’s historical prices on the same date after adjustment for corporate actions. The example contrasts a reported buy price with lower adjusted open and close values. The response explains that platforms may calculate adjustment factors differently and says that underlying real prices are consistent; it suggests using unadjusted real prices when exact price consistency is needed.

This exchange highlights an important data-checking issue for training and backtesting: prices adjusted for corporate actions can vary across providers, so adjusted series may not be directly comparable. It does not identify the platform’s specific adjustment convention, investigate the reported trade, or establish which value is correct. It also provides no methodological detail or broader validation. Researchers should therefore verify whether their data uses adjusted or real prices and ensure trade prices and historical series follow compatible conventions.

Key ideas

• Platforms can produce different adjusted historical prices because their adjustment factors differ.
• The exchange says real, unadjusted prices remain consistent across platforms.
• Comparisons between recorded trades and historical data should account for price adjustment conventions.
• The response does not investigate the example or identify a platform-specific cause.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.