FRM Exam Part I · Insurance Companies and Pension Plans

Property-Casualty Insurance and Underwriting Ratios Explained

Updated 11 October 2026 · Fact-checked

Property-casualty (P&C) insurers cover damage to property and liability claims. You judge their underwriting with ratios: loss ratio = losses ÷ premiums earned, expense ratio = expenses ÷ premiums, combined ratio = loss ratio + expense ratio. Below 100% means an underwriting profit. Operating ratio adjusts the combined ratio for investment income.

Understand Property-Casualty Insurance and Underwriting Ratios

A property-casualty (P&C) insurer sells short-term contracts that pay when insured property is damaged or when the policyholder is legally liable to others. Examples are home, motor, fire, marine, workers' compensation, general liability and professional liability cover. Policies usually run one year and are repriced at renewal. This is a key contrast with life insurance, where contracts are long-term.

The insurer collects premiums up front and pays claims later. Some claims, especially liability claims, can take years to settle. Until then the insurer holds the cash as reserves and invests it. This investment income, often called float income, is a second source of profit besides underwriting.

You measure underwriting performance with ratios. The loss ratio shows how much of each premium dollar goes to claims and claim-adjustment costs. The expense ratio shows how much goes to acquisition costs (commissions), salaries and overhead. Add them and you get the combined ratio. If it is below 100%, the insurer made an underwriting profit. If it is above 100%, it lost money on underwriting and relies on investment income to cover the gap.

The operating ratio goes one step further. It subtracts investment income (as a percentage of premiums) from the combined ratio. An insurer can run a combined ratio above 100% and still have an operating ratio below 100%, meaning it is profitable overall.

The underwriting cycle is the repeating pattern of soft and hard markets. In a soft market, competition and strong capital push premiums down and coverage terms loosen. Underwriting results then worsen and combined ratios rise. Losses, a large catastrophe, or falling investment returns erode capital. Insurers then raise prices and tighten terms, creating a hard market. Higher prices bring profits and new capital, and the cycle turns again.

Key formulas to remember

Loss ratio: Loss ratio = (Incurred losses + Loss adjustment expenses) ÷ Net premiums earned; Some questions use losses only. Use the definition given in the question.
Expense ratio: Expense ratio = Underwriting expenses ÷ Premiums; The denominator can be premiums written or earned. Use the one the question states. Check the wording.
Combined ratio: Combined ratio = Loss ratio + Expense ratio; Below 100% = underwriting profit. Above 100% = underwriting loss.
Operating ratio: Operating ratio = Combined ratio − Investment income ÷ Premiums; Shows overall profitability including investment income. Below 100% = profit overall.
Underwriting profit: Underwriting profit = Premiums × (1 − Combined ratio); Negative result means an underwriting loss.

How to solve Property-Casualty Insurance and Underwriting Ratios questions

Use this method for any P&C ratio question. It keeps the definitions and denominators straight.

1Read the question and list the figures given: premiums, losses, loss adjustment expenses, underwriting expenses, investment income.
2Note whether premiums are written or earned, and use the basis the question specifies for each ratio.
3Compute the loss ratio: losses (plus loss adjustment expenses if stated) ÷ premiums.
4Compute the expense ratio: underwriting expenses ÷ premiums.
5Add the two to get the combined ratio. Compare it with 100%.
6If investment income is given, divide it by premiums and subtract from the combined ratio to get the operating ratio.
7If asked for a profit amount, multiply premiums by (1 − ratio) and keep the sign.
8Check the answer: does the conclusion (profit or loss) match whether the ratio is below or above 100%?

Quickest way: Convert everything to percentages of premiums

When to use it: Use when the question gives dollar amounts for losses, expenses and investment income against a single premium figure.

Divide each item by premiums once: losses %, expenses %, investment income %.
Combined = losses % + expenses %.
Operating = combined − investment income %.
Compare with 100% and pick the option that matches. Eliminate options with the wrong sign first.

Common mistakes in Property-Casualty Insurance and Underwriting Ratios

Treating a combined ratio below 100% as meaning overall profit is certain, or above 100% as meaning overall loss.
Students forget that the combined ratio ignores investment income.
Fix: Combined ratio speaks only to underwriting. Use the operating ratio for overall profitability.
Adding investment income to the combined ratio instead of subtracting it.
Investment income feels like something to add to results.
Fix: Investment income lowers the ratio because it offsets costs. Operating ratio = combined − investment income ratio.
Using the wrong premium base, written instead of earned.
Both figures appear in the question and look similar.
Fix: Use the basis the question names for each ratio. Losses pair naturally with earned premiums.
Forgetting loss adjustment expenses in the loss ratio when they are given.
Students treat them as general expenses.
Fix: If the question defines the loss ratio as including them, add them to losses, and do not count them again in expenses.
Describing a soft market as one with rising prices.
The words soft and hard are confused with demand.
Fix: Soft = low prices, loose terms, weak underwriting results. Hard = high prices, tight terms, recovering profits.

Worked examples

Example 1

A P&C insurer reports net premiums earned of $500 million, incurred losses and loss adjustment expenses of $360 million, and underwriting expenses of $140 million. Investment income is $40 million. Calculate the combined ratio and the operating ratio.

Show the solution

Loss ratio = 360 ÷ 500 = 72%.
Expense ratio = 140 ÷ 500 = 28%.
Combined ratio = 72% + 28% = 100%.
Investment income ratio = 40 ÷ 500 = 8%.
Operating ratio = 100% − 8% = 92%.

Answer: Combined ratio 100% (underwriting break-even); operating ratio 92% (overall profit).

Example 2

An insurer has premiums of $800 million, a loss ratio of 78% and expenses of $208 million. Investment income is $48 million. What is the underwriting result and the operating ratio?

Show the solution

Expense ratio = 208 ÷ 800 = 26%.
Combined ratio = 78% + 26% = 104%.
Underwriting result = 800 × (1 − 1.04) = −$32 million, a loss.
Investment income ratio = 48 ÷ 800 = 6%.
Operating ratio = 104% − 6% = 98%.

Answer: Underwriting loss of $32 million (combined ratio 104%); operating ratio 98%, so the insurer is still profitable overall.

Exam tips

Know the sign logic: below 100% is good for both the combined and operating ratios.
Read the denominator: written versus earned premiums changes the answer.
Expect conceptual questions on the underwriting cycle: soft market means falling prices and rising combined ratios.
Be ready to say why an insurer can have a combined ratio above 100% and still survive: investment income on float.
Do the arithmetic in percentages. Most of these questions take under a minute.

Practice questions from Insurance Companies and Pension Plans

Property-Casualty Insurance and Underwriting Ratios in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

CS ProfessionalUnderwriting in Insurance

Property-Casualty Insurance and Underwriting Ratios: frequently asked questions

What is a good combined ratio for a P&C insurer?

A combined ratio below 100% means the insurer makes an underwriting profit. Many insurers run slightly above 100% and rely on investment income. For the exam, the 100% line is the key benchmark.

What is the difference between the combined ratio and the operating ratio?

The combined ratio is the loss ratio plus the expense ratio and covers underwriting only. The operating ratio subtracts investment income as a percentage of premiums. It shows overall profitability.

What is the underwriting cycle?

It is the repeating swing between soft markets, with low premiums and weak underwriting results, and hard markets, with high premiums and tighter terms. Capital levels, competition and large losses drive the turns.

Why does a P&C insurer earn investment income?

It collects premiums before it pays claims, and liability claims can take years to settle. Meanwhile it invests the reserves. That income can offset an underwriting loss.