Experience modifier,actually explained.

1. What experience mod is

Your experience modifier — usually called "experience mod" or just "mod" — is a multiplier the insurance system applies to your base workers comp premium based on your last three years of claims data. It's how the system priced in the fact that some contractors have cleaner safety records than others.

The logic is simple: businesses with better-than-average claims history get a discount. Businesses with worse-than-average history get a surcharge. Same payroll, same trade, same state — wildly different final premium.

• 1.00 — industry average for your classification. No impact on premium.
• Below 1.00 — clean history. A 0.80 mod means you pay 20% less than the average contractor in your class.
• Above 1.00 — worse-than-average. A 1.30 mod means you pay 30% more.

2. How mod actually gets calculated

The calculation is done by NCCI (the National Council on Compensation Insurance) in most states, using a formula that compares your actual claims history to what would be expected for a business of your size and class.

The inputs:

• Actual losses — what claims have cost over the last 3 years
• Expected losses — what NCCI's data says a business of your size and class should have cost
• Claim frequency vs. severity — lots of small claims weigh differently than one big claim
• A credibility factor — smaller businesses have less statistical weight, so mod moves more slowly

The simplified formula: your actual losses ÷ expected losses = base mod, then adjusted for credibility. The math is more complex than that, but the intuition is right.

Key thing to understand: frequency hurts more than severity. Five $5,000 claims hurt your mod more than one $25,000 claim, even though the total is the same. Carriers view frequency as a signal of systemic safety issues.

3. Why the 3-year window matters

Mod is calculated on a rolling 3-year window, but it excludes the most recent policy period. So your mod at renewal today reflects claims from policy years 4, 3, and 2 years ago — not this past year.

Why the lag? Because claims take time to develop. A $500 claim at the ER can turn into a $50,000 claim after surgery + rehab + lost wages. The system waits for claims to mature before folding them into mod calculations.

Practical implications:

• A bad claim year takes 3 full policy periods to roll off your mod
• A clean year you just finished won't help your mod until two renewals from now
• If you're trying to fix a bad mod, you're playing a long game — not a quick fix
• The single-best thing you can do is prevent new claims while you wait for old ones to age out

4. What mod means in real dollars

Numbers talk. Let's take a GC with $800,000 in payroll at class 5645 (base rate ~$8.50 per $100 payroll). Base premium before mod:

Now watch what mod does:

Between a 0.85 and a 1.15 mod — both reasonable real-world numbers for working GCs — you're talking $20,400 per year differenceon the same payroll. Over 10 years, that's $204,000. Experience mod is where safety programs pay for themselves — often many times over.

5. How to actually lower your mod

Five real levers, ordered by impact:

a. Prevent new claims

The only certain way to improve mod is to stop claims from happening. Written safety program, documented toolbox talks, PPE compliance, hazard-pattern reviews. Every claim you prevent is $5,000–$50,000 not feeding your mod for the next 3 years.

b. Report fast and manage claims actively

When a claim does happen, how you handle it affects cost. A claim reported within 24 hours, with immediate medical care and a documented return-to-light-duty plan, costs the system meaningfully less than a late-reported claim with no employer engagement. Lower cost = less impact on your mod.

c. Audit your own loss runs

Ask your current carrier for a copy of your loss runs (your 3-year claim history). Review every claim. We occasionally find claims incorrectly coded, duplicate entries, or claims closed at inflated reserves when they should have been reduced. Each of those errors may be inflating your mod. Dispute what's wrong.

d. Consider mod correction services

For larger accounts (mods clearly above 1.10 and policies above $100K), there are specialty firms that audit mod calculations for errors and push for corrections. They typically take a percentage of savings. For smaller accounts, the DIY version is item (c) above.

e. Build time into the system

Three clean policy years will roll you toward 1.00 from above. You can't shortcut this — you have to put time in with no new claims. Patience is a strategy.

6. Common mod myths

• Myth: "If I switch carriers my mod resets." Reality: No. Your mod is attached to your business, not your carrier. Every carrier looks at the same calculation.
• Myth: "Small claims don't count." Reality: Every claim counts, and frequency hurts more than severity. Lots of $2,000 claims are worse for mod than one $10,000 claim.
• Myth: "I should avoid filing claims to keep mod low." Reality: Hiding claims is worse. They come out at premium audit or when the employee files directly with the state. Now you have mod hit + carrier trust damage.
• Myth: "Safety programs don't move mod." Reality: Safety programs prevent claims, and claims drive mod. Indirect, but real.

7. When mod hurts your bidding power

Here's a reality most contractors don't hear about until it's hurting them: many commercial GCs require subcontractors to have a mod of 1.0 or below to bid on their jobs. Some require 0.95 or better.

This isn't arbitrary — it's the GC protecting their own workers comp rating. If they bring on a sub with a high mod and that sub has a claim on the GC's job, it impacts the GC's loss history too.

What this means practically:

• If your mod is above 1.0, you may be getting quietly excluded from bids you'd otherwise win
• GCs usually don't tell you why you didn't make the shortlist — they just don't call back
• Improving mod isn't just about premium — it's about the jobs you're eligible for in the first place

8. What to do if your mod just jumped

Every renewal season some contractor opens a quote and sees their mod went from 0.92 to 1.28. Here's what to do:

1. Get your loss runs. Don't accept the mod number without understanding what drove it. Ask your carrier for detailed loss runs covering the last 3 years.
2. Review every claim. Look for coding errors, reserve inflation (claims valued higher than their actual cost), or claims that should have been closed but weren't.
3. Check the dev factor. Ask if any claims have "developed" — meaning their value grew since initial reporting. Sometimes the development is legitimate; sometimes it's aggressive reserving you can push back on.
4. Talk to a specialist. For large jumps, a mod-correction specialist can be worth the consultation cost.
5. Build the safety program. Even if you can't immediately fix the number, start building documentation so your next 3 years compare favorably.
6. Consider state fund if non-renewed. If carriers won't write you, every state has a workers comp state fund (assigned risk pool) that has to accept eligible employers. It's more expensive, but it keeps you insured while you rebuild.

Figures on this page are illustrative. Your premium depends on your state, class codes, payroll, experience modifier, and carrier. Nothing here is a quote or a promise of rate.