diff --git a/docs/replay-run-2-preregistration.md b/docs/replay-run-2-preregistration.md
index 5ff365c..93d4dbd 100644
--- a/docs/replay-run-2-preregistration.md
+++ b/docs/replay-run-2-preregistration.md
@@ -88,6 +88,21 @@ model the base rate will pull it toward the base rate. So:
 Beating run 1 while still sitting below 57.39% is not a system worth trading.
 That distinction gets reported every time, not just when it is convenient.
 
+## Yield is an outcome too, declared before it is known
+
+The brief tells the model that an empty predictions array is always available
+and that it should prefer one on the families it reads worst. So run 2 may
+answer fewer than the 716 articles run 1 answered. Run 1's yield on this set is
+100% by construction, since these are precisely the articles it answered.
+
+Recorded now, with two run-2 proposals on the board and no idea what the rate
+will be: increased selectivity is a real behavioural change and gets reported as
+one, not quietly dropped for shrinking the sample. T4 runs on the shared
+articles whatever that number turns out to be. If the shared set falls below
+about 300 articles the paired test loses the power to see a 5 point shift, and
+the honest report is then "the feedback made it far more selective and the
+sample it left is too small to grade", not a null result dressed up as one.
+
 ## Housekeeping that is easy to forget
 
 Run 2 stays `running` once it exhausts its 716 articles, and the replay lane