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GROWTH-MEASUREMENT ERROR -> PRICE DRIFT  (routing-aware)
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Anchor: BEA advance->third revision avg 0.52pp -> sigma ~0.65pp

One-year price drift from a typical measurement error, by dividend routing:
  (only the kappa_d share hits the goods circuit; floor share is asset-side)
                      mode  kappa_d   to M^T  price drift
    Mode B (floor-weighted)      0.4   0.26%       0.87%
    Mode D (pure dividend)      1.0   0.65%       2.17%
     floor-max (kappa_d=0)      0.0   0.00%       0.00%

  Typical (Mode B) one-year drift: ~0.87%
  Worst case (Mode D) one-year drift: ~2.17%

This is the drift from ONE year's error before the engine re-matches as the
estimate is revised. Stage 2 simulates the multi-year accumulation.
