Workers Compensation Experience Modifier Calculator
Calculate your Workers Compensation Experience Modifier (EMR / X-Mod) — the factor applied to your base premium based on your actual loss history compared to expected losses for your industry.
Formula
The NCCI (National Council on Compensation Insurance) Experience Modifier formula:
EMR = (AP + w·AE + B) / (EP + w·EE + B) Where: AP = Actual Primary Losses (losses capped at the split point per claim, typically $5,000) AE = Actual Excess Losses (losses above the split point per claim) EP = Expected Primary Losses (from payroll × class code primary loss rate) EE = Expected Excess Losses (from payroll × class code excess loss rate) w = Excess Loss Weighting Factor (0–1, assigned by rating bureau based on size) B = Ballast Value (stabilizing constant, assigned by rating bureau) EMR = Experience Modifier Rate (rounded to 3 decimal places)
The modifier is applied to the manual premium: Modified Premium = Manual Premium × EMR
Assumptions & References
- Formula follows the NCCI Experience Rating Plan used in most U.S. states. Some states (CA, NY, TX, PA, NJ, IN, MI, MN, WI, DE, NJ) use independent rating bureaus with similar but slightly different formulas.
- The split point (primary vs. excess loss threshold) is typically $5,000 per claim under NCCI's updated plan (phased in 2013–2015). Some states use different split points.
- The Ballast Value (B) and Weighting Factor (w) are published annually by the rating bureau and vary by expected loss size. Larger employers have higher w values (more credibility given to actual experience).
- Experience rating typically uses 3 years of loss history, excluding the most recent policy year.
- A modifier of 1.00 is average; below 1.00 earns a discount; above 1.00 incurs a surcharge.
- Most states cap the maximum modifier between 1.25 and 2.00 for small employers.
- Employers must meet a minimum premium threshold (varies by state, typically $5,000–$10,000 in manual premium) to be experience-rated.
- Reference: NCCI Experience Rating Plan Manual; state-specific bureaus (WCIRB, NYBCOMP, etc.).