Variance Has a Position: A League-Wide Signal in Box-Score Projection Error

Every projection system is graded on how close its forecasts land — the mean error. We show that the variance of that error carries a structured, position-specific signal the mean does not, and that the signal replicates across leagues and methods in a way that rules out the usual artifact explanations. After conditioning on prior-season production, position, age, and team context, the projection-error variance of blocks for centers is elevated by a factor of 1.26× to 2.03× relative to the rest of the league, and it couples in all 11 testable cells across four leagues — NBA, WNBA, and NCAA Division I men's and women's — under two projection methods that share no machinery.

The signal is selective. Center scoring runs the opposite way (centers are more predictable scorers in all 11 cells), veteran assists show no structure, and a center-rebounding effect that appeared under the simple method dissolves under the hierarchical one — a retraction we report at equal prominence. We argue the block result is the measurable fingerprint of a mechanism the field has understood qualitatively since the Dwight Effect: a block is a noisy proxy for rim deterrence, and a proxy inherits both the variance of the skill it tracks and the variance of its own noise. A forward test on the 2026–27 season is pre-registered.

The variance structure documented here informs how the Resolve NBA and WNBA projections widen their uncertainty bands for center blocks — the position whose error is least like the rest of the league's.