A01 · TOPIC · property-and-casualtyGRA dossier · service level R0
GRAInsurance NexusEstablished
Topic dossier · Insurance Nexus

Property and casualty

Property and casualty insurance covers damage to physical assets and liability to others. Its largest risks are accumulations: many policies hit by one storm, earthquake, flood or wildfire, or many liability claims driven by one product, practice or legal change. This page sets out how catastrophe and portfolio exposure develop, how they are modelled and measured, and which institutions use that evidence for capital, reinsurance and public policy.

The interactive map needs JavaScript; the layer list and sources are below.

Layers 2

Urban signals, for this page

Latest available

NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth

Loading the latest NASA imagery.

Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.

For property and casualty, in GRA's spatial-finance reading, the map opens on population density and night lights with relief in 3D and built-up and settlement extent from NASA GIBS, framed on the Gulf of Mexico coast; every other NASA layer, live feed and forecast waits in the layer list.Satellite and model products as NASA publishes them, each with its own date; indicators, not assessments of any place; claim ceiling INTEGRATED.

Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · GDACS · USGS · CIESIN/Columbia, NASA SEDAC HBASESources and licences

  • We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Center for International Earth Science Information Network (CIESIN), Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11. NASA Socioeconomic Data and Applications Center (SEDAC). Licensed under CC BY 4.0. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). CC BY 4.0
  • VIIRS Black Marble night-time lights, NASA Goddard Space Flight Center; distributed by the NASA Level-1 and Atmosphere Archive and Distribution System (LAADS DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • GPM IMERG precipitation, NASA Precipitation Processing System; distributed by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • NASA Fire Information for Resource Management System (FIRMS), VIIRS 375 m active fire product, NASA LANCE; vector tiles via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
  • © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). ODbL
  • Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
  • Globe: MapLibre GL JS 6.9.1, BSD-3-Clause, © MapLibre contributors.
  • Live: GDACS (EC JRC / UN OCHA) Events are indicative, not official warnings.
  • Live: USGS Events are indicative, not official warnings.
  • Context: CIESIN/Columbia, NASA SEDAC HBASE. Center for International Earth Science Information Network (CIESIN), Columbia University, and NASA Socioeconomic Data and Applications Center (SEDAC): Global Human Built-up And Settlement Extent (HBASE) 2010; Seto, Guneralp and Hutyra 2012, Global Grid of Probabilities of Urban Expansion to 2030; Global Urban Heat Island (UHI) Data Set, 2013.
  • Optional layers (35 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.

Layers and dates

  • Population density, 2020: Population: CIESIN, Columbia University, Gridded Population of the World v4.11 (2018), NASA SEDAC, CC BY 4.0 · static
  • Night-time lights, daily: VIIRS Black Marble (VNP46A2), NASA LAADS DAAC · 12 Oct 2026
  • Flood water, 3-day composite: VIIRS Global Flood Product, NASA LANCE · 14 Oct 2026
  • Land surface temperature, day, 8-day composite: VIIRS NOAA-20 Level 3, 8-day, NASA LANCE · 14 Sep 2026
  • Precipitation rate, daily mean: GPM IMERG, NASA GES DISC · 12 Oct 2026
  • Active fires and thermal anomalies, last day: VIIRS NOAA-20 375 m (FIRMS), NASA LANCE FIRMS · 13 Oct 2026

01In brief

The short answer.

Property and casualty insurance covers damage to physical assets and liability to others. Its largest risks are accumulations: many policies hit by one storm, earthquake, flood or wildfire, or many liability claims driven by one product, practice or legal change. Catastrophe models and exposure data estimate those accumulations for capital and reinsurance decisions.

02Console

Underwriting and claims console, in outline.

The working screen behind this subject: its structure, terms and states. Names are placeholders and values illustrative.

Underwriting and claims console

Property and casualty · Insurer Alpha · Quarter 3

  • Combined ratio, % of NEP
    1014Watch
  • Solvency ratio, % of SCR
    189Normal
  • Rate adequacy
    1.01indexWatch
  • Claims in 30 days, %
    80Normal
Property book above appetiteGRA · Insurance Nexus

Lines of business

Property, commercial21676▲ 7Above
Property, household26166▲ 8Within
Motor21266▲ 0Within
Health14084▲ 5Watch

Loss ratio

Underwriting and claims console: the screen's structure, terms and states for Property and casualty.Placeholder names and illustrative values; a design, not a record or a live system.
03The question

Property and casualty: how the risk develops.

Catastrophe and portfolio exposure. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.

Mechanism

Hazard meets exposure

Loss arises where a hazard footprint overlaps insured values whose vulnerability depends on construction, occupancy, age and local building codes. Exposure data quality often drives model error as much as the hazard does.

Mechanism

Accumulation across a portfolio

Policies that look independent share one event. Accumulation control tracks sums insured by zone and peril, and catastrophe models convert them into event loss tables and exceedance probabilities.

Mechanism

Loss amplification

After a large event, demand surge in labour and materials, prolonged business interruption, contingent supply chain losses and coverage disputes raise the loss beyond the physical damage alone.

Mechanism

Long-tail casualty

Liability claims can emerge years after the policy period through latent injuries, new legal theories, litigation funding and rising awards. Reserves set today absorb that development later.

04Key terms

Terms used on this page.

Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.

TermDefinition
Average annual lossThe expected insured loss per year from a peril, averaged over all simulated years of a catastrophe model.
Probable maximum lossThe loss a portfolio could suffer at a stated return period or exceedance probability, used to size reinsurance and capital.
Exceedance probability curveA curve giving the probability that losses in a year exceed each amount, the main output of a catastrophe model.
Loss amplificationThe rise in claims costs after a large event when demand for labour and materials drives up repair prices and settlement times.
05Indicators

What is measured, and how well.

Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.

IndicatorUnitCadenceSource typeLabel
Average annual losscurrency per yearannualCatastrophe model outputMODELLED
Probable maximum loss at stated return periodcurrencyannualCatastrophe model, occurrence and aggregate exceedanceMODELLED
Total insured value by peril zonecurrencyquarterlyInsurer exposure dataREPORTED
Industry insured loss per eventcurrencyper eventIndustry loss estimation servicesESTIMATED
Prior-year reserve developmentchange in prior-year reserves, currencyannualStatutory loss development trianglesOFFICIAL
Non-modelled peril share of catastrophe lossespercent of catastrophe lossesannualInsurer and broker loss analysisESTIMATED
Exposure data completenesspercent of locations with key attributes codedper portfolioExposure data auditOBSERVED
06Canvas

From sources to decisions.

The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.

Pipeline canvas · Property and casualty as a run graphDesign, not a record
Property and casualty: catastrophe model pipelineA stochastic event catalogue drives the hazard module; exposure and vulnerability turn intensity into damage; the financial module applies policy terms; event and year loss tables give exceedance curves, PML and TVaR. Design of the process, not a record of a run.

Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.

07Sources

Where the evidence comes from.

Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.

SourceWhat it givesLicence class
Verisk Property Claim Services (PCS)Industry insured loss estimates for catastrophe events, used in index triggersProprietary, licensed
Munich Re NatCatSERVICENatural catastrophe event records with economic and insured lossesProprietary; summary statistics published
Swiss Re Institute sigma natural catastrophe reportsInsured and economic catastrophe losses by region and perilProprietary research, reports free to read
Oasis Loss Modelling FrameworkOpen framework for running catastrophe models with exchangeable hazard, vulnerability and exposureOpen source, BSD licence
NOAA IBTrACS and Storm Events DatabaseTropical cyclone tracks and severe weather event recordsPublic domain
Copernicus ERA5 and Emergency Management ServiceReanalysis hazard fields and rapid event footprintsFree and open, attribution
Global Earthquake Model (GEM) hazard and risk mapsOpen seismic hazard and risk modelsCreative Commons, terms per product
OpenFEMA National Flood Insurance Program dataUnited States flood policies and claimsPublic domain
08Decisions

Who decides, and what the evidence serves.

Insurance Nexus prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.

Who decidesThe questionEvidence this page serves
Insurer and reinsurer chief risk officersHow much catastrophe exposure to accept by peril and region, and how much reinsurance to buyExceedance probability curves with model, vendor and data uncertainty shown
Insurance supervisorsWhether internal catastrophe models and accumulation controls are fit for capital purposesModel validation evidence, exposure data quality and scenario losses
Reserving actuaries and audit committeesWhether casualty reserves are adequate given emerging claims trendsLoss development, trend analysis and scenario tests for latent claims
Building code and land-use authoritiesWhere construction standards or zoning would reduce insured and uninsured lossVulnerability evidence and loss differences by construction class

Outputs this topic produces

  • Guide to reading exceedance probability curves and their uncertainty
  • Brief on non-modelled and secondary perils
  • Method note on exposure data quality for accumulation control
  • Evidence-to-diligence checklist for catastrophe model adoption
09Core questions

What professionals ask.

  • How do losses accumulate when one event strikes many insured properties at once?
  • How are catastrophe losses estimated, and how reliable are the estimates?
  • How are exposures changing with urban growth, asset values and climate?
  • How do secondary perils such as floods, hail and wildfire contribute to losses?
  • How do liability and cyber risks create new forms of accumulation?
10Mechanisms

Drivers and dynamics.

Property insurance faces accumulation risk: a single event can produce claims from thousands of policies in the same area. Losses depend on hazard intensity, the location and value of exposures and the vulnerability of buildings. Growth in population and asset values in exposed areas has increased potential losses, independent of changes in hazard. Secondary perils, which individually cause smaller losses, have become significant contributors to annual insured losses.

Casualty and liability risks accumulate differently: through legal trends, latent injuries that emerge years later, and systemic events such as large cyber incidents affecting many firms at once. These risks are harder to model because their drivers include legal and social change as well as physical events.

11Methods and limits

How it is studied.

  1. 01

    Catastrophe models

    Simulating hazard, exposure and vulnerability, drawing on extreme value theory and tail risk and climate and atmospheric science.

  2. 02

    Accumulation analysis

    Measuring concentrations of insured value in areas exposed to the same event.

  3. 03

    Loss data analysis

    Studying past events to calibrate models and understand loss drivers.

  4. 04

    Limits

    Models carry substantial uncertainty for rare events, exposure data is often incomplete, and secondary perils and liability trends are difficult to model.

12Methods

How it is studied, and what the methods cannot say.

13Questions

Questions and answers.

What is a probable maximum loss?
A loss level associated with a stated annual probability of exceedance from a catastrophe model, for one event or for the year's aggregate. It depends on the model, the exposure data and the return period chosen.
Why do two catastrophe models disagree?
They use different hazard catalogues, vulnerability functions and assumptions about demand surge and secondary effects. Disagreement is information about uncertainty; it should be shown, not averaged away.
What is the Oasis Loss Modelling Framework?
An open-source framework, maintained by a not-for-profit company, that runs catastrophe models in a standard format. It lets different hazard and vulnerability components be compared transparently.
What is social inflation?
Growth in liability claim costs beyond general inflation, attributed to litigation trends, larger awards, litigation funding and changing legal doctrines. Its size and causes are debated and vary by jurisdiction.
Why have catastrophe losses grown?
Mainly because more people and more valuable assets are located in exposed areas, with climate change affecting some hazards.
What is a secondary peril?
A hazard such as flood, hail or wildfire that causes frequent, moderate losses, as distinct from major peak perils such as large hurricanes or earthquakes.
Does GRA run catastrophe models for insurers?
No. It studies modelling practice and limits at sector level.
Does GRA give advice on this topic?
No. GRA does not underwrite, sell, solicit, negotiate, place or broker insurance, and it does not rate, advise on or arrange transactions. Readiness work is not approval. Its analysis is shared, sector-level understanding.
Insurance Nexus

Bring your expertise to this field.

The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.

Have questions?