Article Reviewed by a licensed insurance professional: Sam Meenasian (CA dept of insurance license #0F75955).
Estimated reading time: 6 minutes
Understanding your Experience Modification Factor, often called an EMR, E-Mod, or X-Mod, matters because it can materially affect your workers’ compensation premium and can influence how your business is viewed by customers, general contractors, and project owners.
This guide explains what an experience modification is, who calculates it, what goes into the calculation, where to find it, and what you can do if the number seems wrong. For a broader foundation, see our Introduction to Workers Compensation Insurance.
What is an EMF
An Experience Modification Factor is a numeric factor used in workers’ compensation rating that reflects your loss experience compared with expected losses for similar employers in the same classifications. A mod of 1.00 is a unity factor. A mod below 1.00 is a credit mod, and a mod above 1.00 is a debit mod.
Important: Not every employer is experience-rated. In many states, an employer must meet eligibility and minimum data requirements to receive a calculated mod. If those requirements are not met, the employer may receive a unity factor of 1.00 even though the business is not truly average.
EMF, EMR, E-Mod, and X-Mod: are they different
In everyday use, these terms usually refer to the same thing. You may see different names depending on the state and the rating bureau involved, but they generally refer to the experience rating modification applied to workers’ compensation premium calculations.
Who calculates and who uses an experience mod
In most states, the experience mod is produced by the applicable rating bureau, then applied by insurers when rating your policy. For example, NCCI computes and publishes mods in states that have approved and authorized its experience rating plan. Some states use independent rating organizations that produce their own intrastate mods.
Examples of non-insurer entities involved include:
- NCCI states: NCCI acts as the licensed rating and statistical organization in designated states.
- New York: The New York Compensation Insurance Rating Board develops experience modification factors for qualifying employers and sets underwriting rules and classifications in New York.
- California: The WCIRB is a licensed rating bureau and the California Insurance Commissioner’s designated statistical agent, and it administers the experience rating system in California.
Also note that the NCCI Plan does not apply in certain states, including the four monopolistic states of North Dakota, Ohio, Washington, and Wyoming, which administer their own plans and rates.
How an EMF is calculated at a high level
The detailed formulas vary by state and bureau, but most experience rating systems follow the same core logic:
- Define the experience period
The mod is tied to a rating effective date. The experience period is determined by the rating’s effective date and is generally based on about three years of payroll and loss data, excluding the most recent period that is not yet fully valued and reported. - Calculate expected losses based on payroll and class codes
Expected losses are typically derived using your payroll (exposure) and class codes, multiplied by an Expected Loss Rate for each classification. - Separate actual losses into primary and excess portions
A key feature of experience rating is splitting each loss at a state-approved split point. Primary losses (up to the split point) are weighted more heavily and are intended to reflect frequency. Excess losses (above the split point) are weighted differently to reflect severity and limit volatility from large claims. - Apply plan adjustments and stabilizers
Experience rating plans commonly use stabilizing elements so a single claim does not swing the mod too far. In NCCI’s plan, for example, factors like ballast and weighting of excess losses are part of the calculation mechanics. Some plans also treat certain claim types differently. In NCCI’s experience rating plan, medical-only claims are reduced, with only a portion included in the mod calculation, which helps better reflect their impact. - Compute the mod
Conceptually, the mod is derived by dividing adjusted actual losses by adjusted expected losses.
What is a good EMF
A good mod is contextual, but as a rule of thumb:
- Below 1.00: credit mod, generally favorable.
- 1.00: unity factor. It can mean you are average, or that you did not qualify for experience-based rating.
- Above 1.00: debit mod, generally unfavorable and may indicate higher-than-expected loss experience.
If you operate in contractor-heavy markets, you may also have practical good targets driven by bid requirements, prequalification standards, or client expectations.
How the EMF affects your workers’ comp cost
Your experience mod is applied as a factor in premium calculations. A simple example illustrates the potential impact. If a mod factor is 0.75 versus 1.25, the modified premium outcome can differ materially, all else equal.
Important: Your final price is not determined solely by the mod. Classification codes, payroll, state rates, experience rating eligibility, premium discounts, schedule credits, deductibles, and other state-specific rating rules also affect what you pay.
Where to find your EMF
In many cases, your broker or carrier can provide a copy of your current experience rating worksheet and mod factor. The official mod is generally issued by the rating bureau responsible for your state.
Practical tip: Ask for the actual mod worksheet, not just the mod number. The worksheet is what you need to validate payroll, class codes, and the losses included.
What to review on your mod worksheet
When reviewing the worksheet, focus on items that commonly drive errors or misunderstandings:
- Correct business name and entity structure (ownership changes can affect combinability, and which experience is included).
- Correct classification codes and payroll assignment.
- Experience period dates and whether all included policies make sense.
- Claim list accuracy (duplicates, wrong employer, incorrect loss amounts, incorrect claim type).
- Primary vs. excess handling and whether the split-point logic is consistent with the plan.
How to improve an EMF over time
Improving your mod is usually a multi-year effort because experience rating looks back over multiple years. The most effective actions tend to reduce claim frequency and control claim costs early:
- Implement job-specific safety training and enforce it consistently.
- Investigate every incident and fix root causes.
- Report injuries promptly and coordinate with your claims adjuster.
- Use a return-to-work or light-duty program where feasible.
- Review job classifications and payroll processes before the annual audit to avoid surprises.
These steps do not guarantee a particular mod outcome, but they align with how experience rating systems emphasize the frequency and predictability of losses.
Can you challenge your EMF
Yes, but the right process depends on the state, carrier, and rating bureau involved.
Start by documenting the issue and attempting to resolve it with your carrier or agent. In many NCCI states, NCCI provides a field dispute resolution process for disputes about the application of manual rules, including classifications and experience rating.
Examples of issues that can be disputed include applying the correct class codes, allocating payroll among class codes, applying an experience-rating modification factor, and combining the experience of one business with that of another.
The role of business insurance in managing workers’ comp costs
Workers’ compensation is only one part of a business insurance program, but it is one of the most operationally sensitive because payroll, job duties, and claim activity directly influence cost.
If you want a broader overview of other coverages that often connect to hiring, subcontractors, contracts, and jobsite risk, visit our Business Insurance FAQ page.
Need help reviewing your mod
If you want a second set of eyes on your experience rating worksheet, classification approach, and audit prep process, USA Business Insurance can help you understand what is driving the number and what documentation to gather before renewal. Any recommendations should be confirmed against your state’s rules and the applicable rating bureau’s plan.
