Your workers' compensation experience modification factor — often called the "experience mod" or EMR — is a number that compares your business's actual claims history to what would be expected for similar businesses of your size. It directly multiplies your premium: a mod above 1.00 raises your cost, while a mod below 1.00 lowers it. Controlling that number is one of the most powerful ways to control workers' comp spending over time.
Two companies in the same industry, paying the same base rates, can pay very different workers' compensation premiums — and the experience mod is usually why. The mod rewards employers with better-than-average loss records and penalizes those with worse ones, so it functions as both a pricing tool and a financial incentive to run a safer operation. With private-industry employers reporting 2.5 million nonfatal workplace injuries and illnesses in 2024, according to the U.S. Bureau of Labor Statistics, the difference between a good mod and a bad one adds up to real money. Understanding how the factor works is the first step toward managing your workers' compensation insurance costs.
What Is a Workers' Comp Experience Mod?
A workers' comp experience mod is a numerical factor, centered on 1.00, that adjusts your premium up or down based on your company's past claims relative to expected losses for businesses like yours. A mod of 1.00 means your losses are exactly average; below 1.00 means better than average; above 1.00 means worse.
Think of the mod as a report card on your loss history. It is calculated by a rating bureau using several years of your payroll and claims data, then applied as a multiplier to your manual premium. If your manual premium is $50,000 and your mod is 0.90, you pay $45,000; if your mod is 1.20, you pay $60,000 for the exact same coverage. That swing is why larger employers watch the number so closely. Typically, only businesses whose premiums exceed a minimum threshold are large enough to qualify for experience rating at all — smaller employers are pooled at the base rate until they reach that size.
How Is the Experience Modification Factor Calculated?
The experience modification factor is calculated by comparing your business's actual losses over a defined experience period — usually three years, excluding the most recent policy year — against the expected losses for a business of your type and payroll. Rating bureaus weigh the frequency of claims more heavily than the severity of any single claim.
That frequency-over-severity design is important to understand. A pattern of many small claims signals an ongoing safety problem and tends to push a mod higher than one large, unexpected claim of the same total dollar value. In Pennsylvania, experience rating is administered by the Pennsylvania Compensation Rating Bureau (PCRB) rather than the National Council on Compensation Insurance used in most states — one reason PA employers should work with a broker familiar with the state's specific rating rules. The calculation also splits losses into "primary" (the portion of each claim that counts most heavily) and "excess" components, which is why keeping individual claims small has an outsized effect on your final number. Exact formulas and thresholds vary by state and rating bureau.
How Can a Business Lower Its Experience Mod?
A business lowers its experience mod by reducing both the number and cost of claims over time — the mod responds to sustained improvement, not one-time fixes. The most effective levers are preventing injuries in the first place, managing claims aggressively when they do happen, and ensuring the data feeding your mod is accurate.
The mod also matters beyond the premium itself. Many general contractors, facility owners, and public agencies set a maximum experience mod — often 1.00 — as a condition of bidding or being hired, so a high mod can quietly cost a company work, not just money. That makes controlling it a competitive issue as much as an insurance one.
Practical steps include building a documented safety program, training employees consistently, and investigating every incident to eliminate root causes. Equally important is a return-to-work program that brings injured employees back in modified-duty roles as soon as it is medically appropriate — this reduces the "primary" claim costs that drive the mod most. A light-duty assignment that keeps an employee productive during recovery often costs far less, in mod terms, than the same worker sitting fully out on wage-replacement benefits.
Employers should also audit their loss runs and payroll classifications regularly, because errors in reported claims or misclassified job codes can inflate a mod unfairly. Finally, prompt claim reporting and coordinated medical care help control the ultimate cost of each claim. Because a mod reflects several years of history, the businesses that win the long game treat these practices as continuous discipline. Pairing a strong safety culture with the right coverage — and, where relevant, coordinated business liability insurance — protects both your people and your premiums.
Frequently Asked Questions
What is a good workers' comp experience mod? Any experience mod below 1.00 is generally considered good, because it means your business has better-than-average losses and pays a credit on its premium. A mod of exactly 1.00 is average. Consistently strong safety performance can push a mod meaningfully below 1.00 over several years, producing significant savings. What counts as "good" for your specific operation depends on your industry's expected losses.
How many years of claims affect my experience mod? Most experience mods use a three-year window, and importantly, it excludes your most recent completed policy year to allow claims time to develop. That means a bad year continues to affect your mod for roughly three years after it ends — and a good year does the same. Because the effect is multi-year, improving your loss record pays off gradually rather than instantly. Specific periods vary by rating bureau.
Does a single large claim ruin my experience mod? Not as much as many owners fear. Experience rating formulas are built to weigh claim frequency more heavily than the severity of one large, unexpected loss, and they cap how much any single claim can affect the primary portion of your calculation. A pattern of frequent small claims typically damages a mod more than one serious injury. Still, prompt claim management helps limit the impact of any loss.
Who calculates the experience mod in Pennsylvania? In Pennsylvania, the Pennsylvania Compensation Rating Bureau (PCRB) calculates and administers experience modification factors, unlike most states that rely on the National Council on Compensation Insurance. This is why PA employers benefit from working with brokers and insurers who understand PCRB's rules and filings. If you operate in multiple states, more than one rating bureau may be involved, each with its own methodology.
Let Us Help You Manage Your Workers' Comp Costs
Do you have questions about your experience mod or workers' compensation premiums? Contact American Insuring Group for competitive rates and the loss-control resources that help bring your mod down over time. As independent brokers, we shop the market to find the right policy and help you build the safety and claims practices that lower long-term costs.
Call American Insuring Group today at (610) 775-3848 or contact American Insuring Group online. Specifics vary by policy and state — let us help you get it right.
