Split the combined ratio into loss and expense, then attritional and catastrophe, so a deteriorating result is diagnosed correctly. Reach for this on any result question.
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---
name: decompose-the-combined-ratio
description: "Split the combined ratio into loss and expense, then attritional and catastrophe, so a deteriorating result is diagnosed correctly. Reach for this on any result question."
---
# Skill: Decompose the combined ratio
The combined ratio's two (then four) parts each have different fixes.
## Step 1 — Split loss vs expense
Loss ratio and expense ratio separately; under 100 combined is underwriting profit (§3 #1).
## Step 2 — Strip catastrophe
Separate cat load (~7.6 pts in 2025) from the attritional loss ratio (§3 #4).
## Step 3 — Attribute to line of business
Decompose by line — the mix, not the average, tells the story (§3 #6).
## Step 4 — Locate the driver
Name whether the move is expense, attritional loss, cat, or mix before prescribing.
## Output
A loss/expense, attritional/cat, by-line decomposition with the driver located.
