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The experience modifier, or ex mod, is a factor that is developed by examining the insured’s actual loss history against the expected or average loss experience for the insured’s class of business. The calculation returns an experience modifier that will result in either a credit or debit to the insured’s premium.

Whether a company is eligible for experience rating is determined by a number of factors. To determine eligibility, payroll developed during the experience period is totaled by classification code. These totals are multiplied by the expected loss rate for each classification that applies as of the effective date of the experience modification. The sum of these calculations must equal or exceed the minimum eligibility threshold which may change from time to time.

The Workers’ Compensation Insurance Rating Bureau of California (WCIRB) has released its September 1, 2023 Experience Modification Estimator (Estimator). The Estimator is for insurers, agents and brokers to help policyholders understand how payroll and claims experience will affect the computation of their September 1, 2023 and later experience modification (X-Mod).

To use the WCIRB September 1, 2023 Experience Modification Estimator, free of charge, visit the Learning Center on or click on the following link:

– – September 1, 2023 Experience Modification Estimator

By entering policyholder-specific payroll, classification and claims information into the Excel Spreadsheet Estimator, users can obtain an estimated X-Mod using approved September 1, 2023 California Workers’ Compensation Experience Rating Plan – 1995 values (including expected loss rates, D-Ratios and primary thresholds that vary by employer size).

The Estimator’s spreadsheet format makes it easy for users to view and simply copy and paste data into the application. Users can then view, print or save detailed estimated X-Mod information based on that data.

The September 1, 2023 Estimator was updated with the approved experience rating values after the Insurance Commissioner issued a Decision on the WCIRB’s September 1, 2023 Regulatory Filing.

The Estimator is for informational purposes only, and results are approximations based on the information entered. The Estimator does not produce WCIRB-published X-Mods. For more information and helpful tips on how to use the Estimator, go to the WCIRB Experience Modification Estimators page.