The proportional rule is a principle used by insurers to calculate compensation in the event of a claim when the sum insured is less than the actual value of the goods. It is designed to prevent underinsurance.
Example:
The value of your building is $500,000, and the policy requires coverage of at least 80%, or $400,000. You only insure it for $300,000. If a loss causes $100,000 in damage, the calculation will be :
Indemnity = (Amount insured ÷ Amount required) × Damages Indemnity = (300,000 ÷ 400,000) × 100,000 = $75,000
You will receive $75,000 instead of $100,000.
This rule underlines the importance of properly insuring your property to avoid reduced compensation in the event of a claim.