Chapter 10 — Further Reading

Sources grouped by the book's three citation tiers. Tier 1 is verified canonical; Tier 2 is real and attributed but with specifics you should confirm against current editions; Tier 3 is the constructed teaching material in this chapter. Where this chapter only uses an idea owned by another chapter (the loss ratio, the X-mod, GLMs), the deep references live there — this list points to what extends this chapter's math.

Tier 1 — Verified canonical

  • The Institutes (American Institute for CPCU) — AINS, AU, and CPCU curricula. The professional body's materials cover pure premium, loss costs, loss ratios, trend and development, and credibility as core ratemaking and underwriting concepts. The working vocabulary of this chapter is the Institutes' vocabulary; if you pursue a designation, this is where the formal treatment lives.
  • National Council on Compensation Insurance (NCCI) — Experience Rating Plan Manual. The filed, publicly described plan behind the workers'-compensation experience modification factor (the X-mod, Chapter 22) — the largest real-world implementation of credibility weighting, including the primary/excess split and size-scaled credibility discussed in Case Study 1. NCCI also publishes class loss costs (pure premiums).
  • Casualty Actuarial Society (CAS) — credibility and ratemaking literature. The CAS maintains the canonical body of work on credibility theory (classical/limited-fluctuation credibility and Bühlmann/greatest-accuracy credibility) and on loss development and trend. The foundational papers and the CAS study-note tradition are the authoritative source for the §10.5–10.7 material; the classic exposition by Mahler and Dean on credibility is a standard reference.
  • ISO / Verisk. As a statistical and rating organization, ISO develops the loss costs and rating methodologies many carriers build on; the loss-cost concept of §10.3 is ISO/NCCI terminology in practice.
  • Real public pattern — soft-market reserve deficiencies and the underwriting cycle. The recurrence of adverse loss-reserve development on long-tail lines following soft markets (notably the late-1990s/early-2000s soft market) is documented across regulator (NAIC), rating-agency (AM Best, S&P), and actuarial sources, and underlies Case Study 2. Use the pattern as Tier 1; treat any specific company figure as needing verification.

Tier 2 — Attributed, specifics to verify

  • General actuarial and ratemaking texts (e.g., Werner & Modlin, Basic Ratemaking, published by the CAS; and standard pricing references). These give the full mechanics of trend selection, loss development triangles, and the derivation of full-credibility standards. The methods are standard; the worked numbers and parameter choices vary by edition and by line, so confirm specifics against the current text.
  • The "about 1,082 claims" full-credibility benchmark. A specific full-credibility claim count is widely cited for one common confidence/tolerance choice for pure-premium credibility. It is a standard textbook benchmark for a particular set of assumptions, not a universal constant — the required count changes with the confidence level, the tolerance, and the line. Cited here as attributed, with the assumptions noted.
  • Industry loss-ratio, trend, and development data (AM Best, S&P Global, NAIC, and actuarial committee reports). General patterns — that long-tail lines develop upward, that severity trends have run ahead of general inflation in some liability lines ("social inflation") — are well attested; specific annual figures change and must be checked against current sources before use.

Tier 3 — Illustrative / constructed (this chapter)

  • All worked numbers in this chapter — the frequency/severity examples, the loss-ratio "four answers" table, the pure-premium build-ups, the trend/development restatement, the square-root-rule credibility table, and the credibility-weighting calculations — are constructed round numbers chosen to make the mathematics legible. None is drawn from a real account or insurer.
  • The Harbor Steel & Fabrication underwriting file (the two fires, the loss history, and the credibility reading of "two fires in five years") — the constructed progressive-project account, realistic but fictional.
  • Case Study 2's "small-sample book that blew up" — a clearly-labeled composite built from the real, documented soft-market reserve-deficiency pattern; the specific account, figures, and combined ratios are constructed.

If you read only one thing: the NCCI Experience Rating Plan Manual (Tier 1). It is credibility theory made operational at national scale — size-scaled credibility, frequency weighted over severity, single large losses capped — and reading how a filed, regulated plan decides "how much should this risk's own experience move its price" will teach you §10.5–10.7 more concretely than any derivation. Pair it with the CAS credibility literature if you want the theory underneath the plan.