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Established in 1914 by the state legislature, State Fund is California's most reliable provider of workers' compensation insurance and a vital asset to California businesses. State Fund supports California's entrepreneurial spirit and plays a stabilizing role in the economy by providing fairly priced workers' compensation insurance, helping California employers keep their workplaces safe, and restoring injured workers.




Experience Rating Plan Changes

December 29, 2009

“Ex” Marks the Spot: What You Need to Know About New Changes to the Experience Modification Formula

Changes to the California Experience Rating Plan may make a difference in the premiums paid in 2010 and beyond for all California employers who are experience rated. Insurance Commissioner Steve Poizner recently approved revisions to the formula for calculating experience modifications (ex-mods). As California’s workers’ compensation expert, State Fund wants to help everyone learn more about what to expect.

The changes, applicable for ex-mods with rating dates on or after January 1, 2010, will not impact the ratings of all employers in the same way. The degree of change for an individual employer due to the revised formula will largely be determined by the number and size of losses and the employer’s payroll. Most employers will experience a change of a few percentage points under the new methodology. However, greater changes are possible, with larger employers the least affected

What Is Changing—and Why

At the request of Commissioner Poizner, the Workers’ Compensation Insurance Rating Bureau (WCIRB) formed a task force to examine the ex-mod formula in 2007. The group set out to enhance the ex-mod’s predictive value and make it easier to understand, so that employers would more strongly perceive their ex-mod rating as an incentive to manage a safe workplace.

For 2010, the methodology used for splitting actual losses into Primary and Excess components has been changed to the “single split” model used in many other jurisdictions. The first $7,000 of every loss will be considered primary. According to the WCIRB, this change will improve the predictive accuracy of the Experience Rating Plan by approximately 12 percent and is intended to better reflect two statistical tendencies:

  • The incidence of claims is more predictive of an employer’s future losses than the actual size of a given claim, which could be driven by factors beyond an employer’s control. In other words, claims frequency matters more than claims severity.
  • The loss experience of a large employer tends to be more predictive of future losses than that of a small employer.

Projecting the Impact

Each employer’s situation is unique, however, and it is impossible to predict the exact outcome without doing the math. If you have any questions about the changes to the Experience Rating Plan, please contact State Fund.

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