The Experience Modification Rate (EMR), often called the "Ex-Mod," is a critical factor in determining your Workers' Compensation insurance premiums. It is a multiplier that compares your company's claims history against the average for your specific industry.
How the Calculation Works
This calculator uses the standard NCCI (National Council on Compensation Insurance) formula logic to determine your E-Mod. The formula is designed to give more weight to claim frequency (how often accidents happen) than claim severity (the cost of accidents). This is achieved through the "Split Point" concept.
Ap (Actual Primary Losses): The cost of your claims below the split point (usually the first $17,000-$18,500 of any claim).
Ae (Actual Excess Losses): The remaining cost of claims above the split point.
E (Total Expected Losses): What the actuarial tables predict a company of your size and class should lose.
W (Weighting Value): A factor between 0 and 1 that determines how much the "Excess" losses count. Smaller companies have a lower W, meaning they are protected from the volatility of large severity claims.
B (Ballast Value): A stabilizing number added to both the numerator and denominator to prevent extreme swings in the modifier.
Interpreting Your Score
1.0 (Unity): You are exactly average for your industry. You pay the manual premium rate.
Below 1.0 (Credit Mod): Your safety record is better than average. You pay less than the manual rate (e.g., a 0.85 mod means a 15% discount).
Above 1.0 (Debit Mod): Your losses are higher than expected. You pay a surcharge (e.g., a 1.25 mod means a 25% penalty).
Primary vs. Excess Losses
The system penalizes frequency more than severity. For example, ten small injuries costing $10,000 each (Total $100,000) will increase your EMR much more drastically than one large injury costing $100,000. This is because the first $17,000+ of every claim is considered "Primary" and flows into the calculation at 100% value, whereas the amount above that split point is discounted by the Weighting Value.
function calculateEMR() {
// Get input values
var ap = parseFloat(document.getElementById("actualPrimary").value) || 0;
var ae = parseFloat(document.getElementById("actualExcess").value) || 0;
var ep = parseFloat(document.getElementById("expectedPrimary").value) || 0;
var ee = parseFloat(document.getElementById("expectedExcess").value) || 0;
var w = parseFloat(document.getElementById("weightingValue").value) || 0;
var b = parseFloat(document.getElementById("ballastValue").value) || 0;
var manualPremium = parseFloat(document.getElementById("manualPremium").value) || 0;
// Validation for negative numbers
if (ap < 0 || ae < 0 || ep < 0 || ee < 0 || w < 0 || b 0) {
emr = numerator / denominator;
}
var modifiedPremium = manualPremium * emr;
var difference = modifiedPremium – manualPremium;
// Display results
var resultContainer = document.getElementById("resultContainer");
resultContainer.style.display = "block";
var emrElement = document.getElementById("emrResult");
emrElement.innerText = emr.toFixed(2);
// Status Styling
var statusElement = document.getElementById("emrStatus");
if (emr 1.0) {
statusElement.innerText = "Debit Mod (Surcharge)";
statusElement.style.backgroundColor = "#f8d7da";
statusElement.style.color = "#721c24";
emrElement.style.color = "#c0392b";
} else {
statusElement.innerText = "Unity (Average)";
statusElement.style.backgroundColor = "#e2e3e5";
statusElement.style.color = "#383d41";
emrElement.style.color = "#2c3e50";
}
// Financials
document.getElementById("displayManual").innerText = formatCurrency(manualPremium);
document.getElementById("displayModified").innerText = formatCurrency(modifiedPremium);
var diffElement = document.getElementById("displayDiff");
var diffText = formatCurrency(Math.abs(difference));
if (difference 0) {
diffElement.innerText = "+" + diffText;
diffElement.style.color = "#c0392b";
} else {
diffElement.innerText = "$0.00";
diffElement.style.color = "#333";
}
}
function formatCurrency(num) {
return "$" + num.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,');
}