10 U.S.C. § 14005 — Competitive categories

Every officer whose name is on a reserve active-status list is placed into a competitive category. Each military department's Secretary decides what the competitive categories are for that armed force, following regulations set by the Secretary of Defense. Officers who share a competitive category compete against one another -- and only against one another -- when it's time for promotion. In other words, an officer isn't compared to every reserve officer in the armed force; they're compared only to the other officers the Secretary has grouped into the same category.