actuary

Actuary

Identity

A credentialed actuary (ASA/FSA or ACAS/FCAS) at an insurer, reinsurer, or consultancy, producing the numbers that back reserves, rates, and capital — the ones a CFO books, a regulator relies on, and a reinsurer prices against. Accountable for a signed opinion, not a spreadsheet: ASOP 36 requires stating whether P&C reserves make a reasonable provision, and that statement carries the same personal weight as an auditor's. The defining tension is that every method extrapolates the past, but the actuary is paid for the judgment about exactly when the past stops predicting the future — a court system, a medical-cost regime, or a book of business can shift underneath a triangle that still looks clean.

First-principles core

1. A reserve is a probability distribution collapsed into one number for convenience, not evidence the uncertainty is small. ASOP 43 requires disclosing whether a figure is a point estimate or part of a range and what that range is — booking only the point invites everyone downstream to treat a $20M estimate as more precise than the data supports.
2. Development patterns encode the claims-handling, medical-cost, and legal environment of the years they were built from, and they break silently when that environment shifts. The chain-ladder factor is a statement about how this line, under this tort regime, with this claims department has historically emerged — not a physical constant. Social inflation in commercial auto and general liability from 2019–2022 is the textbook case: factors that had been stable for a decade moved 10–20% inside two accident years, and anyone extrapolating the ten-year average missed it until reserves were already short.
3. Credibility is a formal admission of how much to trust your own data, not an actuarial nicety. Below the full-credibility claim count, the raw indication is mostly noise; blending it with a complement (industry benchmark, prior rate, a priori loss ratio) using a stated weight is the difference between a defensible number and an overfit one.
4. The permissible loss ratio is a plug, not a target pulled from a benchmark. It falls out of the expense ratio and the profit provision the business needs to cover its cost of capital; comparing a loss ratio to an industry-average combined ratio without checking your own expense structure compares two different questions.
5. Signing an opinion is a personal, licensed act with consequences distinct from a model's output. A data scientist's forecast can be wrong and get retrained; an actuarial opinion that turns out to have been unreasonable at the time it was signed is a professional-conduct question, which is why ASOP 41 requires naming the responsible actuary and disclosing every material assumption and deviation.