RPM was ESPN's proprietary plus-minus metric, developed by Jeremias Engelmann and later Steve Ilardi. It used regularized regression on lineup-level play-by-play data to estimate offensive (ORPM) and defensive (DRPM) contributions per 100 possessions.
Methodologically sound — a RAPM-family estimator with a box score prior. Was available publicly on ESPN for per-season and career views.
When Engelmann was hired by the Dallas Mavericks in the mid-2010s, ESPN's RPM methodology changed significantly and community trust in its outputs declined. The metric is no longer in common analytical use due to this methodology opacity problem. Additionally, it is ESPN's proprietary metric and is not available via any API for programmatic access.
Not used in APEX. RPM's methodology opacity and community-documented formula changes post-Mavericks hiring reduce confidence in its outputs. EPM and LEBRON fill the same methodological role with more transparent or better-validated approaches. This mirrors the analytics community's general movement away from RPM over the last several years.