What Is the Combined Ratio, and How Insurers Grade Their Own Underwriting

The combined ratio is how a property and casualty (P&C) insurer — think auto, home, or commercial insurance — measures whether the insurance it sold actually made money, separate from whatever it earns investing customers' premiums. It is the insurance-industry equivalent of a retailer asking "did we sell this for more than it cost us," stated as a single percentage.

The formula

Combined ratio = (losses paid + expenses) / premiums earned

This is usually broken into two pieces that insurers report separately:

• Loss ratio: claims paid out (plus money set aside for claims still being settled) as a share of premiums earned.
• Expense ratio: the cost of running the business — commissions, underwriting, administration — as a share of premiums earned.

Combined ratio = loss ratio + expense ratio.

Reading the number

• Below 100%: the insurer collected more in premiums than it paid out in claims and expenses — the underwriting itself was profitable, before any investment returns.
• Above 100%: the insurer paid out more in claims and expenses than it collected in premiums. That is not automatically a crisis — insurers also earn investment income on the premiums they are holding until claims come due, and a slightly-above-100% combined ratio can still leave the company profitable overall — but it means the core insurance business lost money on its own.

A worked example: an insurer collects $500 million in earned premiums, pays $320 million in claims, and spends $150 million running the business. Loss ratio is 64%, expense ratio is 30%, and the combined ratio is 94% — a profitable underwriting year.

What moves it

• Catastrophe losses. Hurricanes, wildfires, and other large-scale disasters show up as a spike in claims in the quarter they occur, often called out separately as "catastrophe losses." A bad quarter for catastrophes can push the combined ratio well above 100% even if the underlying, day-to-day business is healthy — insurers often also report an "ex-catastrophe" or "underlying" combined ratio to show that distinction.
• Pricing (rate) changes. Insurers regularly raise or lower the prices (rates) they charge for coverage. A string of rate increases, once they work through the existing policy base, tends to improve the combined ratio over time.
• Reserve development. Insurers estimate how much they will eventually pay on claims that are reported but not yet settled. If prior estimates turn out to have been too high, releasing those reserves improves the current period's ratio; if they were too low, adding to them worsens it.
• Mix of business. Some lines of insurance (such as auto) typically run tighter combined ratios than others (such as some commercial or specialty lines), so a shift in what an insurer sells more or less of can move the overall number even without any change in pricing or claims behavior.

What to check alongside it

• Net premiums written vs. earned. Written premiums are new and renewed policies sold in the period; earned premiums are the portion of those premiums recognized as revenue so far. A fast-growing insurer can have written premiums well ahead of earned premiums.
• Book value per share. For insurers, this is often a cleaner long-run profitability gauge than net income in any single quarter, since a few outsized catastrophe quarters are normal for the business.

Life and health insurers, and insurance brokers, generally don't report a combined ratio — it's specific to insurers that write P&C-style policies with claims that can be estimated and settled against a defined premium.