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Shifted return pairing changes a slope

Rotating the original asset series one row changes its fitted slope from 2.1 to zero.

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Compare original and shifted pairing

Original pairing-error example
Benchmark (%)Correct asset (%)Rotated asset (%)
-2-3-0.5
-1-0.51
012.5
12.56
26-3

Keep the individual series summaries

The rotated asset list contains the same five numbers, so its mean and centered squared sum are unchanged. Benchmark values are also unchanged. The cross-products change because the period pairing changes.

Read the resulting slope

Correct pairing gives centered cross-product 21 and slope 2.1. The rotated cross-product is zero, giving slope zero and intercept still 1.2%. Marginal means alone cannot detect the mismatch.

Use actual period evidence

Retain matching dates or period identities. If one observation is missing, remove the complete pair or apply a documented treatment; do not independently shorten one list and shift subsequent observations. The example is hypothetical, not a recommendation to rearrange data to improve a fit.

Further references