Answer: Daily returns prior to the most recent day are reflected in the EWMA calculation by the previous variance rate estimate.

## Explanation In the Exponentially Weighted Moving Average (EWMA) model for volatility estimation, the formula is: \[ \sigma_t^2 = \lambda \sigma_{t-1}^2 + (1-\lambda) r_{t-1}^2 \] Where: - \(\sigma_t^2\) = current variance rate estimate - \(\sigma_{t-1}^2\) = previous variance rate estimate - \(r_{t-1}^2\) = most recent day's squared return - \(\lambda\) = smoothing parameter (decay factor) The key insight is that the **previous variance rate estimate** \(\sigma_{t-1}^2\) already incorporates information from all historical returns prior to the most recent day. This is because the EWMA model is recursive - each day's variance estimate depends on the previous day's variance estimate, which in turn depends on returns from even earlier days. Therefore, daily returns prior to the most recent day are reflected in the EWMA calculation through the **previous variance rate estimate**, making option D correct. **Why other options are incorrect:** - **A**: Incorrect - Prior returns do influence the current estimate through the recursive structure - **B**: Incorrect - The smoothing parameter λ determines the decay rate but doesn't directly contain prior return information - **C**: Incorrect - The most recent day's squared return only contains information about that specific day, not prior days

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