How Experience Mod Rate Is Calculated

Understanding how experience mod rate is calculated gives brokers a direct advantage in every workers' compensation renewal conversation. The NCCI formula compares an employer's actual losses against the losses a business of that size and class "should" have generated, then produces a multiplier applied directly to manual premium. The 2026 NCCI split point is $18,500 per claim. Every dollar of a claim up to $18,500 counts as primary loss at full weight. Every dollar above $18,500 counts as excess loss at a fraction of its value.

This post walks through the formula, each variable, a worked example, and the state-level variations brokers need to know.

Key Takeaways

• The NCCI EMR formula for 2026 is: (Actual Primary Losses + Weighted Actual Excess Losses + Ballast) / (Expected Primary Losses + Weighted Expected Excess Losses + Ballast)
• The current NCCI split point is $18,500 per claim as of 2026, up from $10,000 in 2013, meaning more of each claim now counts as full-weight primary loss
• Primary losses carry 100% weight; excess losses carry only 7-30% weight depending on employer size, making claim frequency far more damaging than claim severity
• NCCI publishes Expected Loss Rates (ELRs) and D-Ratios annually by class code; these determine the denominator of the EMR formula
• A ballast value stabilizes the formula for small employers, limiting the swing from any single large claim
• Seven states (California, New York, New Jersey, Texas, Delaware, Indiana, Wisconsin) operate their own rating bureaus with formulas that differ from NCCI in split point thresholds and credibility tables

The NCCI EMR Formula

NCCI (National Council on Compensation Insurance) defines the experience modification rate with this formula (NCCI 2025):

EMR = (Ap + W x Ae + B) / (Ep + W x Ee + B)

Where:

• Ap = Actual Primary Losses
• Ae = Actual Excess Losses
• Ep = Expected Primary Losses
• Ee = Expected Excess Losses
• W = Weighting Value (depends on employer size)
• B = Ballast Value (stabilizing factor)

An EMR of exactly 1.0 means the employer's actual losses matched what NCCI expected for a business of that type and size. Below 1.0 is better than average. Above 1.0 is worse than average.

The Five Variables Explained

Actual Primary Losses (Ap)

The first $18,500 of each claim incurred during the experience period. If a claim's total incurred value is $12,000, the entire $12,000 is primary. If a claim is $45,000, only $18,500 qualifies as primary. These losses carry 100% weight in the numerator.

Actual Excess Losses (Ae)

The portion of each claim above $18,500. For a $45,000 claim, the excess is $26,500. Excess losses are multiplied by the weighting factor W. For a small employer with $50,000 in expected losses, W may be as low as 0.10, meaning only $2,650 of that $26,500 excess contributes to the numerator.

Expected Primary and Excess Losses (Ep and Ee)

NCCI calculates expected losses by multiplying the employer's payroll in each class code by that code's Expected Loss Rate (ELR), then splitting using the D-Ratio (Discount Ratio). The ELR is the average loss rate per $100 of payroll for all employers in that classification nationwide. NCCI updates ELRs and D-Ratios annually. The D-Ratio represents the fraction of expected losses that fall in the primary layer.

Ballast Value (B)

The ballast is a stabilizing constant derived from the employer's expected loss total. Smaller employers get a higher ballast relative to their expected losses, which pulls the EMR toward 1.00 and reduces volatility from any single claim. Larger employers get a lower ballast, making their EMR more responsive to actual loss experience. The ballast is what prevents a small employer with one catastrophic claim from receiving an EMR of 5.0.

Weighting Value (W)

W determines how much of the excess losses actually affects the EMR. A small employer with $20,000 in expected losses might have a W of 0.07. A large employer with $500,000 in expected losses might have a W of 0.28. This is why severity matters less than frequency for smaller employers: the excess portion of a large claim is nearly invisible in their formula.

Step-by-Step Calculation with Real Numbers

Consider a plumbing contractor with the following profile:

Business profile:

• Class code 5183 (Plumbing, Heating, Refrigeration): $500,000 payroll over the experience period
• ELR for class 5183: 2.15 per $100 of payroll (NCCI 2025 published rate)
• D-Ratio for class 5183: 0.31

Step 1: Calculate total expected losses.

Expected losses = ($500,000 / 100) x 2.15 = $10,750

Step 2: Split expected losses into primary and excess.

• Expected Primary Losses (Ep) = $10,750 x 0.31 = $3,333
• Expected Excess Losses (Ee) = $10,750 x 0.69 = $7,418

Step 3: Identify claims in the experience period.

Three claims occurred in the 2022-2024 experience period:

• Claim A: $7,000 incurred (sprained ankle)
• Claim B: $25,000 incurred (hand laceration with surgery)
• Claim C: $4,500 incurred (back strain)

Step 4: Split actual losses into primary and excess.

• Claim A: Primary = $7,000, Excess = $0
• Claim B: Primary = $18,500, Excess = $6,500
• Claim C: Primary = $4,500, Excess = $0
• Total Actual Primary (Ap) = $30,000
• Total Actual Excess (Ae) = $6,500

Step 5: Determine W and B values.

For an employer with $10,750 in expected losses, NCCI tables assign approximately:

• W = 0.08
• B = $9,400

Step 6: Calculate the EMR.

• Numerator = Ap + (W x Ae) + B = $30,000 + (0.08 x $6,500) + $9,400 = $39,920
• Denominator = Ep + (W x Ee) + B = $3,333 + (0.08 x $7,418) + $9,400 = $13,326
• EMR = $39,920 / $13,326 = 1.30

This employer pays 30% above the base workers' comp rate. On a $15,000 manual premium, that equals $4,500 in additional annual cost. On a $50,000 manual premium, it equals $15,000 extra per year.

Now run the same employer with no claims:

• Numerator = $0 + (0.08 x $0) + $9,400 = $9,400
• Denominator = $3,333 + (0.08 x $7,418) + $9,400 = $13,326
• EMR = $9,400 / $13,326 = 0.71

Zero claims produces an EMR of 0.71, a 29% savings on manual premium.

EMR Impact on Modified Premium

The EMR multiplies directly against manual premium to produce modified premium.

Modified Premium = Manual Premium x EMR

Every 0.01 change in EMR equals a 1% change in premium. A move from 1.30 to 1.00 saves 23% on annual workers' comp cost.

The Split Point: How It Has Changed Over Time

The split point is the threshold that separates primary from excess loss treatment. NCCI has raised it steadily since 2013 (NCCI 2025):

As the split point rises, more dollars from each claim convert from excess (reduced weight) to primary (full weight). This makes the EMR slightly more sensitive to mid-size claims. A $20,000 claim in 2013 had $10,000 primary and $10,000 excess. The same claim in 2026 has $18,500 primary and $1,500 excess. More of the claim now hits at full weight.

How Employer Size Changes the Formula

NCCI scales the weighting factor and ballast based on employer size, measured by the level of expected losses:

Small employers get a high ballast that anchors the mod near 1.00. A single $50,000 claim won't push a small employer's EMR above 1.35-1.40 because the ballast absorbs most of the numerator increase.

Large employers have a tiny ballast relative to their losses. A bad accident year can push their EMR to 1.50+. Conversely, three clean years can produce a mod of 0.65-0.70.

The Experience Period: Which Years Are Included

The experience period covers three full policy years, excluding the most recent completed year. In 2026, when NCCI issues the experience mod effective for the upcoming renewal, the experience period is policy years 2022, 2023, and 2024. The 2025 policy year is excluded because losses are still developing and carriers have not yet submitted final Unit Statistical Reports.

This lag creates a planning opportunity. A clean 2025 will not show in the EMR until the 2027 modification. Understanding which years are in and out of the period helps brokers project future EMR movement for clients.

State-Level Variations

Most U.S. states use NCCI's formula and data. Seven states operate independent rating bureaus with distinct formulas (NCCI 2025):

Brokers with clients operating in multiple states need to obtain EMR worksheets from each applicable bureau. A contractor working in California and Nevada has separate EMRs from WCIRB and NCCI. The worksheets will differ in both structure and output.

Reserve Development and Open Claims

Open claims affect the EMR based on their total incurred value: paid losses plus outstanding reserves. Carriers set initial reserves conservatively, often 30-50% above the probable ultimate cost (NCCI 2025).

A claim reported as a back injury may receive an initial reserve of $28,000. If the employee recovers quickly and the claim closes at $11,000, the reserve reduction changes the EMR calculation significantly:

• At $28,000: primary loss = $18,500, excess = $9,500
• At $11,000: primary loss = $11,000, excess = $0

The difference is $7,500 in primary loss weight and $9,500 in excess loss weight. For a mid-size employer, this reserve reduction alone can move the EMR by 0.04-0.06 points.

Brokers who request reserve reviews on open claims, provide return-to-work documentation, and follow up on claim closures produce measurable EMR reductions. The highest-value target: any open claim with reserves between $15,000 and $30,000, where the split-point boundary amplifies every dollar of reserve movement.

For strategies to bring these numbers down, see reducing experience modification rate. For a factor-by-factor breakdown of what moves the EMR, read experience mod rate factors explained.

FAQ

What is the current NCCI split point for experience mod rate calculation?

The NCCI split point for 2026 is $18,500 per claim. This threshold divides each claim into a primary loss component (the first $18,500, weighted at 100%) and an excess loss component (anything above $18,500, weighted at 7-30% depending on employer size). The split point was $10,000 in 2013 and has been raised incrementally. NCCI adjusts it periodically to reflect medical cost inflation and loss trend data.

How many years of losses go into the experience mod rate calculation?

The experience mod rate uses three full policy years, but excludes the most recent completed policy year. In 2026, the experience period is 2022, 2023, and 2024. The 2025 policy year is excluded because loss development is still in progress and carriers have not yet filed final Unit Statistical Reports with NCCI. This creates a 12-24 month lag between a loss event and its full appearance in the EMR.

What does an experience mod rate of 1.0 mean?

An EMR of 1.0 means the employer's actual losses exactly matched what NCCI expected for a business of that size and classification code. It is the industry average benchmark. An EMR below 1.0 means the employer had fewer losses than expected and pays less than the manual rate. An EMR above 1.0 means they had more losses than expected and pay a surcharge. The dollar impact is direct: a 1.0 EMR on $200,000 manual premium produces $200,000 in modified premium.

How does the ballast value affect experience mod rate for small employers?

The ballast value is a stabilizing constant added to both the numerator and denominator of the EMR formula. For small employers with low expected losses, the ballast is large relative to their losses, which limits the swing from any single claim. A small employer with $15,000 in expected losses might have a ballast of $25,000. A single large claim cannot push their EMR above approximately 1.35-1.40 because the ballast absorbs most of the shock. As expected losses grow, the ballast shrinks and the employer's EMR becomes more credible.

Do all states use the NCCI experience mod rate formula?

No. Thirty-six states plus the District of Columbia use NCCI's formula and data directly. Seven states operate independent rating bureaus: California (WCIRB), New York (NYBCOICF), New Jersey (NJCRIB), Texas, Delaware (DCRB), Indiana (ICRB), and Wisconsin (WCRB). These bureaus use formulas that are structurally similar to NCCI's but differ in split point thresholds, ELR tables, credibility parameters, and eligibility criteria. Brokers with multi-state clients need separate worksheets from each applicable bureau.

How does one large workers' comp claim affect the experience mod rate?

A single large claim affects the EMR primarily through the primary loss layer. On a $75,000 claim, only the first $18,500 counts at full weight. The remaining $56,500 counts at 7-30% depending on employer size. For a small employer with a W factor of 0.08, that $56,500 excess contributes only $4,520 to the numerator. Compare this to three $25,000 claims: each contributes $18,500 in primary loss at full weight, totaling $55,500. Three smaller claims cause more EMR damage than one large claim of equivalent total cost. Frequency is the more damaging pattern.

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Written by Javier Sanz, Founder of BrokerageAudit. Last updated April 2026.