Several things have happened in California that will effect the cost of Workers’ Compensation in 2012. The first major item is the increase in the pure premium rate by California Insurance Commissioner Dave Jones. The new rate, in combination with the removal of previous reforms, adds up to approximately a 37% increase in premiums. The second major change is how California determines its experience rating formula.
The experience modification factor is one of the biggest influences on your workers’ compensation insurance premiums. It is a complex formula that is based on your loss history and payroll data to determine your rates.
Until 2012, the formula looked like this:
X-Mod = {Ap + (W x Ae) + [(1 - W) x Ee + B} / (E + B)
Ap = Actual primary losses; Ae = Actual excess losses; E = Expected losses; Ee = Expected excess losses; B = Ballast and W = Weight
In 2012, according to the WCIRB, the "change does away with ballast and weighting values in favor of credibility primary and credibility excess factors:
Credibility primary factors (Cp) are used to weigh a risk’s actual primary losses, which are a measure of loss frequency. The larger a risk is (as measured by expected losses), the greater weight that is given to primary losses.
Credibility excess factors (Ce) are used to weigh a risk’s actual excess losses, which are a measure of loss severity. Again, the larger a risk, the greater the weight. Notably, very small risks have such little predictive value in this area that Ce will actually be zero."
So the new formula now looks like this:
Modification =[(Ap x Cp) + (Ep x (1 – Cp))] + [(Ae x Ce) + (Ee x (1 –Ce))] / E
Ap = Actual Primary Losses
Cp = Credibility Primary Value
Ep = Expected Primary Losses
Ae = Actual Excess Losses
Ce = Credibility Excess Value
Ee = Expected Excess Losses
E = Expected Losses
If this formula doesn’t make sense to you, don’t worry. What is important is that a Workers’ Compensation insurance agent can help explain it to you and how your rate is determined.
Basically, the fewer losses you have, the less your premium will be. However, factors such as your industry, the types of workers you have, and how long you have been in business will affect this rate.
To learn more about Experience Modifications and how they affect your Workers’ Compensation Insurance premium, click here.









