“Lagging metrics measure actual past events, such as device or SIF failures, as a way to compare rates of occurrence. Failure rates may be compared with other periods of time within the facility’s history to identify trends, or other facilities within the industry to gauge relative performance”
Reference: Barnard, G.S., Safety Instrumented Systems, in Handbook of Loss Prevention Engineering. 2013, Wiley-VCH Verlag GmbH & Co. KGaA. p. 590.
Examples include OSHA reportable incidents, fatalities, loss of containment above a certain threshold, as per API RP 754.