Known Issue 427

Coverage back-allocation is improved with NGM for event totals (e.g. byEvent table, byLayer table). This leads to a mismatch between coverage losses within byEvent / byLayer table and coverages in byLocation tables (byLocation still uses the pre-NGM logic).

Issue ID	427
Summary	Coverage back-allocation is improved with NGM for event totals (e.g. byEvent table, byLayer table). This leads to a mismatch between coverage losses within byEvent / byLayer table and coverages in byLocation tables (byLocation still uses the pre-NGM logic).
Description	Coverage back-allocation is improved with NGM for event totals (e.g. byEvent table, byLayer table). This leads to a mismatch between coverage losses within byEvent / byLayer table and coverages in byLocation tables (byLocation still uses the pre-NGM logic). The accuracy improvement of back-allocation is for layered exposures. Non-layered exposures are not affected and do not have such an accuracy issue.
Resolved in	Touchstone 2025 (13.0)
Date posted	11/21/2024
Software versions affected	12.2.3, 12.2, 12.0, 11.5, 11.0
Feature set	Detailed loss results
Models
Potential for loss numbers impact	Yes
Workaround	If accurate by coverage splits are required, use the event total tables (byEvent, byLayer). Coverage splits within byLocation table are still using the pre-NGM method.