World Series probability points added per acquired WAR. Same acquisition stack as PPA, but measured on the championship curve.
CPA is the championship sibling of PPA. Every established-MLB acquisition is graded once, in the season its wins first reach the roster. Instead of asking how much the move changed playoff odds, CPA asks how much it changed World Series odds.
The unit is championship probability points per acquired WAR. A CPA of 0.50 means the GM historically bought about half a World Series percentage point for every acquired WAR, given the roster contexts where those acquisitions landed.
World Series odds also rise with roster WAR, but the curve is much flatter than the playoff curve because October is high variance. Fit a logistic on full team-seasons since 1985:
\[ P(\text{World Series}\mid W) = \sigma(\alpha_c + \beta_c W) \]In the current fit, a 40-WAR team is roughly a 2% title team, 45 WAR is roughly 4%, 50 WAR is roughly 8%, and 55 WAR is roughly 14%. Even great teams do not become overwhelming title favorites.
For a season's acquisition class, start from the roster already on hand, then stack each new acquisition's arrival-year WAR onto that base. The class's title boost is:
\[ \text{championship boost} = \big[\,P_c(W) - P_c(\text{base})\,\big]\times 100 \]That boost is split with the same Shapley method used for PPA, so the player-level credits add exactly to the season's total. No one player gets full credit for a threshold crossing created by the whole class.
\[ \text{CPA} = \frac{\sum_\text{deals}\text{Shapley}_\text{championship}}{\sum w}\quad\text{(championship points per bought WAR)} \]CPA is still a realized metric, not an ex-ante forecast. Bad acquisitions that produce little or no positive WAR receive little or no CPA, but the metric is not yet comparing expected points at the time of acquisition to realized points afterward.
Fit on full team-seasons (≥100 games), 1985–2024/25. All figures are franchise-level outcomes credited to the decision-maker in the relevant year — see the GM profiles for per-executive numbers.