The signed quarterly delta measuring whether an organization is above or below the cognitive equilibrium line — a formal measurement requirement in the entity engineering methodology. Calculated by comparing the corroboration signal count, parametric recall rate, and citation coverage from the prior quarter against the current quarter. A positive delta indicates the organization is above the cognitive equilibrium line (defended posture); a negative delta indicates it is below (contested posture, regardless of what the monitoring dashboard shows). The schema entropy rate makes the defense line visible and actionable rather than merely conceptual — closing the contested-posture-invisibility failure mode at the measurement level.