# reinsurance.dev

> A reinsurance analytics tutorial for software engineers: contract, portfolio, and pricing analytics for property cat reinsurance, built on cat model output.

Source: https://reinsurance.dev/

## Find a topic

**Foundations: [The industry](https://reinsurance.dev/foundations/)**

- [The market](https://reinsurance.dev/foundations/the-market/)
- [Market participants](https://reinsurance.dev/foundations/market-participants/)
- [Products and contracts](https://reinsurance.dev/foundations/products-and-contracts/)
- [Perspectives on loss](https://reinsurance.dev/foundations/products-and-contracts/#perspectives-on-loss)
- [Personas](https://reinsurance.dev/foundations/personas/)

**Analytics Toolkit: [Trials and loss tables](https://reinsurance.dev/toolkit/trials/)**

- [What is a trial?](https://reinsurance.dev/toolkit/trials/#what-is-a-trial)
- [Events and occurrences](https://reinsurance.dev/toolkit/trials/#events-and-occurrences)
- [The Year Event Loss Table (YELT)](https://reinsurance.dev/toolkit/trials/#the-yelt)
- [Event Loss Tables](https://reinsurance.dev/toolkit/trials/#event-loss-tables)

**Analytics Toolkit: [Curves and metrics](https://reinsurance.dev/toolkit/metrics/)**

- [Exceedance probability (EP) curves](https://reinsurance.dev/toolkit/distributions/)
- [Occurrence (OEP) vs. aggregate (AEP)](https://reinsurance.dev/toolkit/distributions/#oep-vs-aep)
- [Expected loss (EL)](https://reinsurance.dev/toolkit/metrics/expected-loss/)
- [Value at Risk (VaR)](https://reinsurance.dev/toolkit/metrics/value-at-risk/)
- [Tail Value at Risk (TVaR)](https://reinsurance.dev/toolkit/metrics/tail-value-at-risk/)
- [Attachment and exhaustion probability](https://reinsurance.dev/toolkit/metrics/attachment-and-exhaustion-probability/)

**Financial Modelling: [Terms](https://reinsurance.dev/financial-modelling/terms/)**

- [Loss filter](https://reinsurance.dev/financial-modelling/terms/filter/)
- [Contract period](https://reinsurance.dev/financial-modelling/terms/contract-period/)
- [Occurrence excess](https://reinsurance.dev/financial-modelling/terms/occurrence-excess/)
- [Aggregate excess](https://reinsurance.dev/financial-modelling/terms/aggregate-excess/)
- [Scaling](https://reinsurance.dev/financial-modelling/terms/scaling/)

**Financial Modelling: [Contracts](https://reinsurance.dev/financial-modelling/contracts/)**

- [Quota share](https://reinsurance.dev/financial-modelling/contracts/quota-share/)
- [Catastrophe excess of loss (CatXoL)](https://reinsurance.dev/financial-modelling/contracts/catxol/)
- [Aggregate excess of loss (AggXoL)](https://reinsurance.dev/financial-modelling/contracts/aggxol/)
- [Dissecting a contract](https://reinsurance.dev/financial-modelling/dissection/)
- [Contracts as compositions](https://reinsurance.dev/financial-modelling/composition/)

**Financial Modelling: [Programs and portfolios](https://reinsurance.dev/financial-modelling/)**

- [Financial perspectives](https://reinsurance.dev/financial-modelling/perspectives/)
- [Programs](https://reinsurance.dev/financial-modelling/programs/)
- [Portfolios](https://reinsurance.dev/financial-modelling/portfolios/)

**Financial Modelling: [Beyond loss](https://reinsurance.dev/financial-modelling/beyond-loss/)**

- [Flows that are not loss](https://reinsurance.dev/financial-modelling/beyond-loss/)
- [Reinstatement premium](https://reinsurance.dev/financial-modelling/beyond-loss/reinstatement-premium/)
- [Two reinstatements, and a clause pro rata to time](https://reinsurance.dev/financial-modelling/beyond-loss/reinstatement-premium/#two-reinstatements-and-a-clause-pro-rata-to-time)
- [Pricing with reinstatement premium](https://reinsurance.dev/applications/standalone-pricing/#step-4-reinstatement-premium-in-the-price)

**Applications: [Business decisions](https://reinsurance.dev/applications/)**

- [Risk profiling: the post-model report](https://reinsurance.dev/applications/risk-profiling/)
- [Standalone program pricing](https://reinsurance.dev/applications/standalone-pricing/)
- [Portfolio analytics](https://reinsurance.dev/applications/portfolio-analytics/)
- [At production scale](https://reinsurance.dev/applications/production-scale/)

**Reference: [Caldera Re](https://reinsurance.dev/caldera-re/)**

- [Company profile](https://reinsurance.dev/caldera-re/#company-profile)
- [The portfolio: six contracts](https://reinsurance.dev/caldera-re/#portfolio)
- [Data files](https://reinsurance.dev/caldera-re/data/)

**Reference: [Vocabulary and conventions](https://reinsurance.dev/glossary/)**

- [Glossary](https://reinsurance.dev/glossary/)
- [Scope, conventions & assumptions](https://reinsurance.dev/conventions/)
- [Sign convention](https://reinsurance.dev/toolkit/trials/#sign-convention)

## Who this is for

This site is written for software engineers who are new to reinsurance: the backend engineer who has just joined a reinsurer with strong software skills and no insurance background, the senior engineer pivoting from fintech, the architect modernising a legacy risk system. It assumes you can read Python and reason about probability. It assumes nothing about insurance. Actuaries will find the mathematics stated precisely; engineers will find every formula that computes a number paired with the code that computes it.

## Scope

**Property-catastrophe reinsurance, after the model has run.** Everything on this site starts from the [catastrophe model](https://reinsurance.dev/glossary/#catastrophe-model)'s loss output (thousands of simulated futures, each a **[trial](https://reinsurance.dev/glossary/#trial)** in the vocabulary the [Analytics Toolkit](https://reinsurance.dev/toolkit/trials/) defines) and works downstream: how contracts transform loss, how portfolios aggregate it, and how prices and capital derive from it. The focus is deliberate. Property cat is the line where a single event can cost the industry tens of billions.[^cat-losses] This site chose it because the loss data is rich enough, and the contracts intricate enough, to make the analytics an engineering problem in their own right.

[^cat-losses]: Insurance Information Institute, ["Facts + Statistics: Global catastrophes"](https://www.iii.org/fact-statistic/facts-statistics-global-catastrophes), citing Aon data as of January 2026. Its table of the ten costliest world natural disasters by insured loss, 1900 to 2025, is headed by Hurricane Katrina at \$65 billion insured (\$107 billion in 2025 dollars) and Hurricane Ian at \$54 billion.

:::note[Not covered, by design]
The following topics are outside this site's scope. Each is a discipline of its own with its own methods and literature. They sit either upstream of the cat model's loss output or outside property catastrophe:

- **Catastrophe-model internals**: hazard, vulnerability, and event-generation modules. This site consumes the model's loss output; it does not explain how the model produces it.
- **Exposure rating and exposure curves**: pricing from exposure profiles rather than model output.
- **Experience rating**: pricing from a [cedent](https://reinsurance.dev/glossary/#cedent)'s historical losses.
- **Reserving and IBNR (incurred but not reported)**: estimating liabilities for losses that have already occurred.
- **Casualty, specialty, life, and health reinsurance**: lines whose analytics rest on different foundations than simulated catastrophe output.

If a question sits upstream of the model's loss output, or outside property cat, the question is out of scope here.
:::

The scope statement defines the subjects this site covers. Other conventions (vocabulary, the sign convention, units, loss perspectives, capital) are indexed on one page, [Scope, conventions & assumptions](https://reinsurance.dev/conventions/), each with a pointer to the section that explains it.

## How the site is organised

Four chapters, in reading order, and three reference pages the chapters draw on throughout:

```mermaid
graph TB
    F[Foundations<br/>the industry: market, participants, contracts, people]:::Losses --> T[Analytics Toolkit<br/>measuring a loss distribution: trials, EP curves, metrics]:::Process
    T --> M[Financial Modelling<br/>transforming loss: terms, contracts, programs, portfolios]:::Contract
    M --> A[Applications<br/>business decisions: profiling, pricing, portfolio analytics]:::Metric
    R[Caldera Re · Glossary · Conventions<br/>reference pages shared by all four]:::Neutral -.-> F

    classDef Losses fill:#F5CEBC,stroke:#B16C4B,stroke-width:1.5px,color:#2B2620
    classDef Contract fill:#BFDBF8,stroke:#4F84BA,stroke-width:1.5px,color:#2B2620
    classDef Process fill:#F7CBCB,stroke:#B46669,stroke-width:1.5px,color:#2B2620
    classDef Metric fill:#BDE2CB,stroke:#459269,stroke-width:1.5px,color:#2B2620
    classDef Neutral fill:#E7E0D9,stroke:#97918A,stroke-width:1.5px,color:#2B2620
```

A single fictional reinsurer, **[Caldera Re](https://reinsurance.dev/caldera-re/)**, appears in every chapter: six contracts, five cedents, and a 20-trial loss dataset small enough to check by hand. The numbers recur from page to page, so a figure in the Toolkit is the same loss that a contract transforms in Financial Modelling and a pricing story prices in Applications.