MLB
120 franchises, 1254 managerial tenures, and the win-share change across every handover. The last column is the difference between a manager and the predecessor at that franchise — descriptive, not causal: rosters, schedules and eras move alongside a hire. It is withheld entirely when either tenure ran under two seasons, because differencing two noisy numbers produces a confident-looking figure built from nothing.
Derived from data/mlb/coach-careers.json, built 2026-10-06. 454 of 1254 handovers met the two-season floor. A tenure is every season a manager ran the franchise, including a later return.