Underwriting Profit and the Combined Ratio
The single number insurers use to tell whether the core business of writing policies made money on its own — before counting investment returns — and why a combined ratio above 100% doesn't necessarily mean an insurer is losing money overall.
Prerequisites: How an Insurance Balance Sheet Works
An insurer takes in premiums and pays out claims, but the timing gap between the two — premiums arrive up front, claims trickle out over months or years — means the company also earns investment income on the money sitting in between. That creates a genuine question: is the insurer's core business, writing and pricing policies, actually profitable on its own, or is it only surviving because of the returns it earns investing the "float"? The combined ratio answers exactly that question, deliberately ignoring investment income so the underwriting business can be judged on its own merits.
How the combined ratio is built
The combined ratio is the sum of two pieces, both expressed as a percentage of earned premium: the loss ratio (claims paid out, plus reserves set aside for claims still developing, divided by premium earned) and the expense ratio (the cost of acquiring and administering policies — commissions, underwriting staff, overhead — divided by premium earned). Add them together and you get the combined ratio. A combined ratio under 100% means the insurer collected more in premium than it paid out in claims and expenses — an underwriting profit, standing entirely on its own before any investment return is added. A combined ratio over 100% means an underwriting loss — the insurer paid out more in claims and expenses than it earned in premium — but the company can still be profitable overall if investment income on the float more than covers the gap.
For example, an insurer with a 65% loss ratio and a 30% expense ratio has a 95% combined ratio — a 5-point underwriting profit. A different insurer with a 70% loss ratio and 33% expense ratio has a 103% combined ratio — a 3-point underwriting loss on paper — but if that insurer earns a 5% return on a large investment float, it can still post a solid overall profit; the combined ratio alone doesn't tell you that story either way.
What this means in practice
Comparing combined ratios across insurers or across years is one of the fastest ways to judge underwriting discipline, independent of how favorable the current investment climate happens to be — a period of low interest rates squeezes float income, so insurers that were relying on investment returns to offset underwriting losses get exposed much faster than ones with a genuinely profitable underwriting book.
The combined ratio (loss ratio plus expense ratio, as a share of premium) measures whether an insurer's core underwriting business is profitable on its own, deliberately excluding investment income — a ratio above 100% is an underwriting loss, but the company can still be profitable overall if float income covers the gap.
A combined ratio just above 100% is often read as "this insurer is losing money," which isn't quite right — it means the underwriting business alone lost money, but investment income on premiums held between collection and claims payment can still make the company profitable overall. The two need to be looked at separately, not conflated.
Further reading
- Cummins & Weiss, Analyzing Firm Performance in the Insurance Industry