# Loss ratio and its cousins: pure, incurred and paid, calculated side by side
A regional auto insurer reports a "loss ratio of 62%" in its quarterly investor call. Three analysts on the line write down three different numbers in their models, because none of them asked which loss ratio the CFO meant. That confusion costs real money when it feeds into pricing decisions or stock valuations.
Loss ratio sounds like one number. It is actually a family of related metrics, each answering a slightly different question. Let's build all three from the same simple book of business.
A loss ratio measures claims costs as a share of premium. In its simplest form:
Loss ratio = Losses ÷ Premium
It tells you what fraction of the money an insurer collects gets paid back out in claims. A loss ratio of 70% means 70 cents of every premium dollar goes to claims, leaving 30 cents for expenses, profit and reserves.
But "losses" is doing a lot of work in that formula. Losses can mean money already paid, money owed but not yet paid, or a pure actuarial estimate of expected claims. That's where the cousins come in.
Imagine a book of 1,000 personal auto policies, each with an annual premium of $1,200. Total earned premium (premium the insurer has "earned" by providing coverage for the period, as opposed to premium simply billed) is:
1,000 × $1,200 = $1,200,000
During the year, 80 policyholders file claims. Here's what happens to those claims by year-end:
Separately, the actuarial team, before knowing any actual claims experience, had priced the book assuming an expected loss cost of $650,000 for the year, based on historical loss trends for this driver segment.
The pure loss ratio (also called the expected or burning cost ratio) uses only the actuarially projected losses, calculated before or independent of actual claims experience. It's a pricing tool, not a reporting tool.
Pure loss ratio = Expected losses ÷ Earned premium
= $650,000 ÷ $1,200,000
= 54.2%
Actuaries use this figure when setting rates for the next policy period. It answers: "given everything we know about this risk pool's history, what loss ratio should we expect?" It never appears in a financial statement. It lives in pricing models and rate filings submitted to regulators like state insurance departments in the US or, in Europe, under Solvency II technical pricing requirements.
The incurred loss ratio is the one you see most often in earnings reports. Incurred losses = losses paid + case reserves + IBNR. It captures everything the insurer currently believes it owes, whether or not the cash has moved yet.
Incurred losses = $420,000 (paid) + $280,000 (case reserves) + $90,000 (IBNR)
= $790,000
Incurred loss ratio = $790,000 ÷ $1,200,000
= 65.8%
This is the number analysts scrutinize most, because it reflects management's current best estimate of total claims cost for the period. It's also the number most exposed to reserve development: if those 20 open claims later settle for more or less than $280,000, next quarter's incurred loss ratio for this accident year will move, even though nothing "new" happened.
The paid loss ratio only counts claims actually disbursed. No estimates, no reserves.
Paid loss ratio = Paid losses ÷ Earned premium
= $420,000 ÷ $1,200,000
= 35.0%
This is the most conservative and least "opinionated" figure because it contains no actuarial judgment. But it's also the most misleading if read alone, since it ignores $370,000 of claims the insurer already knows it owes. A paid loss ratio always understates ultimate cost early in a claim's life cycle, especially for lines with long settlement tails like commercial liability or workers' compensation, where claims can take years to close.
| Metric | Formula basis | Result |
|---|---|---|
| Pure loss ratio | Actuarial expected losses | 54.2% |
| Incurred loss ratio | Paid + case reserves + IBNR | 65.8% |
| Paid loss ratio | Cash paid only | 35.0% |
Same book, same year, three legitimate answers ranging almost 31 points apart. None is "wrong." They answer different questions: what did we expect to happen, what do we now believe happened, and what has actually left the bank so far.
When a US public insurer reports its combined ratio (loss ratio plus expense ratio, where anything under 100% signals underwriting profit) under GAAP (Generally Accepted Accounting Principles), the loss ratio component is almost always the incurred loss ratio for the accident year, sometimes adjusted for prior-year reserve development. The US property and casualty industry's average combined ratio has hovered in the high 90s to low 100s in recent years (estimate, varies by line and year; source: III Insurance Information Institute).
In Europe, insurers reporting under IFRS 17 (the international accounting standard for insurance contracts effective since 2023) disclose a related but distinctly calculated figure often called the loss ratio or claims ratio within the combined ratio, built from the insurance service expense line rather than raw cash payments. European motor insurers often target combined ratios similar to US peers, generally in the 90s to around 100%, though this varies significantly by country and market conditions (estimate).
The lesson: never compare loss ratios across two companies, or two countries, without confirming they're built the same way.
Knowledge check
1. Why did three analysts on the same earnings call potentially write down three different numbers after hearing 'loss ratio of 62%'?
2. What is the key conceptual difference between case reserves and IBNR estimates within an incurred loss calculation?
3. An insurer wants to know how much cash has actually left the company for claims during the year, independent of future obligations. Which version of the loss ratio should it examine?
4. Select ALL correct answers about what 'losses' can represent in a loss ratio calculation.
Select all the correct answers.
5. Select ALL correct answers about why distinguishing between paid and incurred loss ratios matters for pricing or valuation decisions.
Select all the correct answers.
One more wrinkle worth knowing. If, a year later, those 20 open claims actually settle for $310,000 instead of the $280,000 reserved, the insurer records adverse reserve development of $30,000. This flows through as additional incurred losses in the year it's recognized, not restated into the original year. That's why an insurer's reported loss ratio for a given accident year can keep drifting upward (or downward, with favorable development) for several years after the policy period closes. Long-tail lines like general liability or medical malpractice often take 5 to 10 years to fully "mature."
Simple reserve development check:
Original reserve estimate: $280,000
Actual settlement amount: $310,000
Development (adverse if +): $30,000🎬 [VIDEO: "Loss Ratios Explained" - youtube.com - search for insurance-industry explainer channels covering loss ratio, combined ratio and reserve development for a visual walkthrough of these mechanics]