Insurance float

An insurer is paid before it performs. Premiums arrive at the start of a policy and claims are paid later, sometimes decades later on long tail liability business. The money held in between is the insurance float, and the investment return earned on it belongs to the insurer.

This is why an insurer contains two businesses with two cycles. Underwriting is priced against expected claims and moves with competition and rates charged. Investing is a function of the size and duration of the float and the yields available in the market. Reading a headline profit without separating them tells you very little about either.

Duration is what separates the two main insurance models. A general insurer's float turns over quickly, so its investment income responds to current yields fairly soon. A life insurer holds liabilities for decades, so the analysis becomes one of matching asset and liability duration, and a mismatch there is a solvency question rather than a margin question.

The float is not free money. It is held against liabilities that are estimates, and an insurer that underprices policies to grow the float is buying investment income with underwriting losses. Whether that trade works depends on the yield available, which is not something the insurer controls, so it is a strategy with a hidden dependence on the rate environment.