case reserves vs bulk reserves

Picture a claims department after a storm. For each individual claim that lands on a desk — this dented roof, that flooded basement — an adjuster looks at the file and writes down a best guess of what it will eventually cost. That hand-set, claim-by-claim estimate is a case reserve. Now picture the chief actuary standing back from the whole pile, knowing from experience that adjusters' guesses are usually a bit low and that some claims have not even arrived yet, and adding one big extra cushion on top of everyone's individual numbers. That extra cushion, set in aggregate rather than claim by claim, is a bulk reserve.

Precisely, a case reserve is an estimate set on a specific, known, reported claim — usually by a claims adjuster from the facts of that file, sometimes by a formula. A bulk reserve (also called a bulk-and-IBNR provision) is an amount the actuary adds at the portfolio level to cover what the case reserves miss: claims not yet reported at all (pure IBNR) and the tendency of open case reserves to develop upward over time (IBNER). For example, if 500 open claims carry case reserves of 20 million but history says this kind of business ultimately costs 28 million once everything is reported and re-estimated, the actuary books an 8 million bulk reserve so the total reflects the expected ultimate, not just what is visible today.

The distinction matters because the two are produced by different people using different information and going stale at different rates. Case reserves are granular and current but individually noisy and systematically optimistic on long-tail lines; bulk reserves are coarse but capture the things no single adjuster can see. A frequent confusion is to think bulk reserves and IBNR are exactly the same — IBNR strictly means claims not yet reported, while bulk reserves in practice often also include the expected upward movement of claims that have already been reported.