Experience modification rate: the number that prices your payroll

An experience modification rate — the mod, or EMR — is a factor applied to a workers compensation premium reflecting how an employer’s actual claims compare with what is expected for a business of its size and classification. An average employer sits at 1.00; below that reduces the premium, above it increases it.

It is computed by a rating bureau from data the carriers report, not by the employer or the broker, over an experience period covering several past policy years and excluding the most recent one. That lag has a consequence worth internalising: a bad year keeps affecting the premium for years after the safety problem is fixed, and this year’s improvements will not show up for a while.

Frequency matters more than severity

• The calculation weights the first portion of each claim more heavily than the remainder, so many small claims raise the mod more than one large one of the same total value.
• That is deliberate: frequency is treated as a better predictor of future losses than severity, which is partly random.
• The practical implication is that a business with a stream of minor recordable injuries can carry a worse mod than one with a single serious claim.
• Open reserves count. A claim reserved at a high figure affects the mod before anybody knows what it will settle for.
• Medical-only claims are typically discounted in the calculation, which is why keeping an injury from becoming a lost-time claim matters disproportionately.

The experience modification rate is not only about premium

In construction and industrial contracting the mod is a qualification threshold as well as a price. Owners and general contractors commonly set a maximum — frequently around 1.0 — for bidding eligibility, so a mod that drifts above it removes a contractor from work entirely rather than merely costing more. That makes the number a commercial metric owned by the business, not an insurance detail owned by the broker.

Check the worksheet the rating bureau issues rather than accepting the factor. Claims attributed to the wrong entity, stale reserves and misapplied classifications all appear in it, and they are correctable — but only if somebody reads it, and it usually arrives shortly before renewal.

What actually moves it

Two things, over time. Reducing the number of claims, particularly the small lost-time ones — which is a return-to-work programme and prompt reporting rather than a poster campaign, and which shows up first in the osha 300 log. And managing reserves: reporting claims immediately so they are investigated while facts are available, and challenging reserves that clearly exceed the likely outcome. Neither works quickly, because of the lag, which is the argument for starting before the number becomes a problem rather than after a contract is lost.

Tracking it as a number you own

The employers who manage this well keep their own record: claims by year with dates, status, paid and reserved, alongside the mod worksheets as issued. Ettex Sheets holds that history so a trend and an error are both visible, Ettex Records keeps the worksheets and the correspondence correcting them, and the reports the figures come from are covered in loss runs.

To be clear: this is a spreadsheet and a records file, not insurance advice. The calculation belongs to the rating bureau, the reserves to the carrier, and your broker is the route for challenging either.