Prologue — When Risk Maps Set the Price
The price of homeowners insurance can double even though the house has not changed in appearance, ownership or use. The house has suffered no loss. Sometimes a new map is enough to place the address in a more exposed zone. The insurer may then raise the premium, impose new conditions or stop offering the policy.1
The Morenos had bought their home in Altadena, California, in the early 2000s. Pasadena was still close, and the San Gabriel Mountains were visible from the street. Their 1920s bungalow had three bedrooms, a porch, a garage and a garden planted with a few agaves. It was not a luxurious property, but a family home with land and light.
For years, homeowners insurance had been an ordinary household expense. It cost about $2,400 in 2023. The renewal quotation rose to nearly $4,100 in 2024. The insurer then announced that it would no longer offer a policy. The broker mentioned the cost of reinsurance, a difficult market and the area’s new classification. He also used an industry expression. Mainstream insurers no longer had much “appetite”2 for the neighbourhood.
By the end of 2024, the Morenos had to turn to the California FAIR Plan, California’s insurance scheme of last resort.3 With the additional cover needed alongside its basic fire policy, the annual cost approached $8,200. The protection was narrower and the deductibles4 were higher [1].
On 7 January 2025, the Eaton Fire began near Altadena [2]. Part of the community was devastated, but the Morenos’ block remained standing. California’s insurance commissioner then imposed a one-year moratorium on cancellations and non-renewals within the fire perimeter and nearby areas. The measure protected policies that were still in force. It could not restore the ordinary-market policy the Morenos had already lost [3].
They had seen the smoke and heard the sirens. No wall of their house had burned. Yet their address now occupied a different place in the insurance market.
Thousands of miles away, the same mechanism could take a less dramatic form. The Faures had bought a 1930s house on the hills of Saint-Étienne in the early 2000s. It had beige stucco, a tiled roof, a sloping garden, a garage partly below ground and a basement office fitted out during the Covid-19 pandemic. Nothing marked the neighbourhood as a particularly threatened area.
After heavy rain, the storm drains became overwhelmed. Farther down the street, basements filled with water and furniture emerged coated in mud. The water did not cross the Faures’ doorstep. Insurers nevertheless stopped looking at the address in the same way.
The premium, below €500 in 2023, rose to about €670. The following year, a broker offered a policy costing close to €760. The family would have to install a backflow valve, raise the boiler and stop listing the basement office as living space. It was becoming difficult, the broker said, to obtain several quotations in the neighbourhood.
The family home had suffered no damage. In underwriting systems, it was now an address in a “blue zone”. The risk had not yet produced a claim at the Faures’ home. It had already changed their contract.
From Map to Contract
A map does not raise a premium by itself. It becomes decisive when an institution connects a colour, class or score to a consequence. This process extends beyond California and France.
In the United Kingdom, Flood Re allows insurers to transfer part of the flood risk of eligible homes to a common scheme in order to preserve access to cover [4]. Across the Caribbean, Africa and the Pacific, regional mechanisms release funds quickly to governments when a hurricane, earthquake or drought crosses a threshold defined by a model [5].
The contracts differ, but they rely on a similar operation. An estimate made before a loss changes the terms of a future payment. A wildfire map may raise a premium. A flood zone may require work. Under parametric insurance5 purchased by a government, a drought index crossing a threshold may trigger a payment for emergency assistance.
When risk rises, the insurer must account for expected losses, reconstruction costs and reinsurance. A premium that remains too low can weaken its ability to pay. A sharp increase, however, can make coverage unaffordable, lead households to give it up or prompt insurers to withdraw [6–8].
The effects do not remain within the policy. A high premium can make a sale more difficult, weaken a mortgage, lead a household to reduce its cover or hasten its departure. Flooding can also lower property prices and increase the time needed to sell a home [9]. The map then affects whether people can remain in a place.
To become usable, a map simplifies a complex territory. It selects a scale, period, event, scenario and resolution. It then draws boundaries and assigns classes. These choices make the territory legible to a public authority or a company [10]. They also shape what the map shows and what it leaves outside the frame [11]. Even a satellite image must be dated, documented and interpreted before it becomes information for action [12].
Fire, water and the shrinking and swelling of clay soils are real. The exact boundary between a red zone and an orange one does not exist in nature in a ready-made form. It depends on the scenario, the period and the threshold selected. Its significance depends above all on what the institution attaches to the colour. The consequence may be protective work, financial assistance, a higher premium, a lending condition or non-renewal.
A map can save lives and guide investment. It is not enough when it merely announces the price of danger without providing the means to reduce exposure.
The Judgement behind the Price
Risk does not arrive on an actuary’s6 desk ready to be priced. Categories, observation periods, coverage, thresholds and underwriting rules7 must all be chosen. Two insurers may therefore classify the same house differently. They do not have the same portfolio8 or the same strategy. The physical hazard remains, but these choices shape the contract that covers it [13].
Statistics give the decision a numerical and impersonal form. They do not determine which variables are admissible, where thresholds should be placed or which consequences should follow from each category. Nineteenth-century British actuaries already had mortality tables and formulas. Those instruments did not tell them which lives to accept, which rate to charge or how to interpret the particular experience of a portfolio [14].
Judgement has not disappeared from contemporary models. It has been distributed across data, code, underwriting rules and automated procedures. This makes it harder to identify. Law acts before the price appears. It determines who may sell insurance, what can be covered, which duties bind the parties and which routes of appeal remain open [15].
Insurance law and regulation also shape coverage, permitted variables, cancellation rules and the capital a company must hold. They do not simply correct a market that already exists in finished form. They help construct it.
A price may reveal a genuine market limit. It may also move that limit. A house remains insured, but a higher premium weakens the mortgage. A policy continues, but with a larger deductible and narrower cover. A decision made within insurance then affects credit, property values and the possibility of remaining in the neighbourhood.
References
Composite scenes bring together observed situations, published cases and documented orders of magnitude. They do not describe identifiable people and do not constitute evidence. Documented cases are identified as such and accompanied by sources.↩︎
In insurance, risk appetite refers to the types and levels of risk that a company is willing to cover.↩︎
The California FAIR Plan, whose name stands for Fair Access to Insurance Requirements, is California’s property insurance scheme of last resort. It provides basic cover to owners who cannot find a policy in the ordinary market. It is administered by an association of property insurers licensed in the state.↩︎
In property insurance, a deductible is the part of a covered loss that the policyholder must pay.↩︎
Parametric insurance pays a sum fixed in advance when a measurable indicator crosses a threshold set in the contract. Payment depends on that indicator, such as rainfall or wind speed, rather than on a detailed assessment of each loss.↩︎
An actuary is a professional who translates risk into financial quantities. Actuaries estimate claim probabilities, premiums and the future cost of commitments. Their work helps determine what a risk costs and how that cost will be shared.↩︎
In insurance, underwriting is the process of examining a risk and deciding whether to accept it, reject it or cover it under specified conditions.↩︎
An insurer’s portfolio is the set of policies and risks it covers at a given time.↩︎