Loss ratio and its cousins: pure, incurred and paid, calculated side by side

• 50 claims are fully paid, totaling $420,000 in actual cash paid out.
• 20 claims are reported but still open (in litigation, awaiting repair estimates, etc.). The insurer's claims adjusters estimate these will ultimately cost $280,000. These estimates sit in case reserves.
• 10 claims are IBNR (incurred but not reported, meaning the accident happened but the claim hasn't been filed yet). Actuaries estimate $90,000 for these based on historical patterns.

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.

Pure loss ratio: the actuary's starting point

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.

Incurred loss ratio: the full picture, including estimates

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.

Paid loss ratio: cash out the door, nothing more

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.

Side by side

| 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.

Why this matters for reading real company numbers

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.

A quick data check-in: reserve development

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]

Key Takeaways

• Pure loss ratio is a pricing input (expected losses ÷ premium), used by actuaries before the policy year even starts. It never appears in financial statements.
• Incurred loss ratio (paid + reserves + IBNR, divided by earned premium) is the standard figure in earnings reports and combined ratio calculations; it reflects current best estimates, including unpaid claims.
• Paid loss ratio counts only cash disbursed and will always run lower than incurred early in a claim's life, especially for long-tail lines like liability or workers' compensation.
• Always confirm which loss ratio, and which accounting basis (GAAP incurred vs. IFRS 17 claims ratio), before comparing figures across companies, countries, or time periods.
• Watch for reserve development: a rising incurred loss ratio in later periods for the same accident year signals the original claims estimates were too low, a red flag worth investigating in any insurer's filings.