How do you interpolate deductible credit factors in General Liability insurance?

GL Deductible credits are given based off of ISO (Insurance Services Office - an advisory and data gathering organization) credit tables depending on class of business, but most often are used by judgement of the underwriter.

The standard deductible we think about in everyday life usually relate to OUR possessions. Those deductibles in insurance (homeowners, auto) are taken OFF the ultimate payment, therefore giving the Insurer the almost undeniable ability to collect.

GL Deductibles are recuperated from insureds AFTER payment. That is because on GL deductibles are paid to third parties, so the disbursement can not be garnished in the same way that property deductibles are.

Also, General Liability losses tend to have much more severity to them. For the 2 reasons listed, GL credit factors tend to be somewhat negligible until you are starting to get into very high levels of insured risk retention.