Because the rating period is fixed, the damage from one claim has an end date you can count. What varies is how much of the increase was real in the first place. A meaningful share of sharp jumps trace back to data rather than to safety, and data can be corrected — but only if somebody goes and looks.
What is worth checking before you accept the number:
Reserves nobody revisited. Claims are valued at a fixed point in time. A reserve set high early and never adjusted downward as the claim developed stays in the calculation at the high figure.
Payroll classified into the wrong code. Installation and service work do not always belong under one classification, and a shop doing both sometimes files everything under the higher-rated one. This inflates expected losses and the mod along with them.
Claims that closed for far less than reserved. If the closure happened after the valuation date, the worksheet still carries the old number until the next one.
Medical-only claims at full value. California applies a reduction to medical-only claims in the calculation. It should be reflected; occasionally it is not.
How Liberty structures your protection:
Liberty pulls the rating worksheet and audits it against the actual claim and payroll records before the renewal is marketed, because a correction found at that stage changes the premium every carrier quotes.