Case: adding a 'save this' line raised reach 27%

Case: adding a 'save this' line raised reach 27%
A productivity account (44k) appended an explicit save prompt to 30 carousels, vs 30 without. Randomized.
— No prompt: save rate 1.8%, median reach 6,400
— With prompt: save rate 3.4%, median reach 8,130 (+27%)
— Comments and likes were statistically flat between cohorts
Saves were the only metric that moved — and the only one that moved reach.
So what: the CTA worked because it targeted the exact signal the ranking system rewards, not vanity engagement. (n=60 posts, 50-day window)