Industry Loss Warranty: When ILWs Beat Indemnity Cover

Industry Loss Warranties: When an ILW Beats Indemnity Reinsurance on Cost and Basis Risk

Last reviewed: November 2026

An industry loss warranty (ILW) is a contract that pays when insured losses across the whole industry from one event exceed an agreed trigger, such as USD 30 billion for US hurricane. In reinsurance form, it also requires the buyer to suffer an ultimate net loss of its own, which makes it a dual-trigger cover.

ILWs can be cheaper and faster to place than indemnity reinsurance, but they pay on the industry's loss, not yours. Whether that trade works depends on how closely your own losses track the index.

This guide is for heads of retro and outwards reinsurance, CROs, cat modellers and CUOs. It explains how ILWs work, how to measure basis risk, and when an ILW is the better buy.

Key Takeaways

• An industry loss warranty pays on an industry loss index, not on the buyer's own loss, so it trades precision for cost and speed.
• Dual-trigger ILWs add an ultimate net loss condition, which usually allows reinsurance accounting and capital treatment.
• Basis risk cuts both ways: the buyer can suffer a large loss with no recovery, or recover more than its own layer loss.
• Binary ILWs pay the full limit at the trigger, while pro rata ILWs pay progressively and reduce the cliff-edge effect.
• The index provider, such as PCS or PERILS, and its reporting timetable decide when and how much the ILW pays.
• An ILW beats indemnity cover only when the premium saving outweighs the cost of the basis-risk scenarios that matter most.

What Is an Industry Loss Warranty?

An industry loss warranty is a catastrophe cover whose payout depends on an industry-wide insured loss estimate for a defined peril, territory and period. The buyer chooses a limit and an industry trigger, and the seller pays when the trigger is reached.

Most ILWs used as reinsurance include two triggers:

• Industry loss trigger: the industry insured loss estimate for the event must reach or exceed the agreed level.
• Ultimate net loss (UNL) trigger: the buyer must suffer its own net loss from the same event, and recoveries are usually capped at that loss.

The UNL trigger is often set low, because its job is to establish indemnity rather than to define the layer. A contract with only the industry trigger is closer to a derivative than reinsurance.

Which Indices Do ILWs Use?

ILWs reference an independent industry loss estimate. The two most widely used providers are Property Claim Services (PCS), owned by Verisk, and PERILS AG, based in Zurich.

PERILS states that its reporting closes no later than 36 months after the event. Always check the provider's current methodology, because thresholds, territories and peril definitions change over time.

How Does an ILW Differ From Indemnity Reinsurance?

An ILW pays on the industry's loss, while indemnity reinsurance pays on the cedent's own loss. That single difference drives price, data needs, speed and basis risk.

The key insight is that sellers price an ILW on the industry distribution, which they can model well and diversify. They do not need to underwrite your book, and that is where the saving comes from.

How Is an ILW Priced?

An ILW is priced mainly from the probability that industry losses exceed the trigger, using vendor and in-house catastrophe models. The seller then adds a margin for capital, uncertainty and market conditions.

Three features move the price:

1. Trigger level. A higher industry trigger means a lower probability of payment and a lower rate on line.
2. Territory and peril scope. An ILW covering all US perils costs more than one covering only Florida hurricane at the same trigger.
3. Payout form. A binary ILW and a pro rata ILW with the same attachment have different expected losses, so they are priced differently.

Binary or Pro Rata?

A binary ILW pays the full limit as soon as the trigger is hit. A pro rata ILW pays a share of the limit that rises in line with the industry loss between attachment and exhaustion.

Binary covers are simple but create a cliff edge just below the trigger. Pro rata covers behave more like an indemnity layer and usually reduce basis risk for a book that tracks the market.

Can Basis Risk Be Reduced?

Basis risk can be reduced by narrowing the index to the buyer's footprint. Options include regional triggers, peril-specific triggers and weighted indices.

PERILS notes that structured triggers using loss weighting factors can significantly reduce basis risk. The trade-off is more complex documentation and less liquidity.

Worked Example: ILW vs Indemnity Under Four Storms

The example below is illustrative and simplified. Cedent losses are in USD millions, industry losses are in USD billions, and rates are assumptions, not market quotes.

Buyer: a regional property writer whose US hurricane losses have historically run at about 0.2% of industry losses. On that ratio, each USD 1 billion of industry loss produces about USD 2 million of loss to the buyer.

Options for the same USD 20 million of cover:

The ILW triggers are chosen so that, at a 0.2% share, an industry loss of USD 30bn implies a buyer loss of 60, the indemnity attachment. An industry loss of USD 40bn implies a buyer loss of 80, the indemnity exhaustion point.

Four storm outcomes:

In storm 1, the binary ILW over-recovers by 10 compared with indemnity, while the pro rata ILW matches indemnity exactly. In storm 3, both ILWs pay 20 although the buyer's own loss of 40 sits below the indemnity retention.

Storm 2 is the scenario that matters. The buyer suffers its worst loss of the four, 85, and both ILWs pay nothing because the industry loss stops at USD 28bn.

If a storm 2 outcome has an annual probability well below 1-in-25, the binary ILW looks cheaper on expected cost. But the shortfall lands in exactly the year the buyer most needs capital, so expected cost alone understates the risk.

The lesson for buyers: test the ILW against your own concentrated-loss scenarios, not just against the industry curve. An ILW beats indemnity cover when your loss share is stable across events and the remaining basis risk sits in scenarios your capital can absorb.

The lesson for sellers: positive basis risk, as in storm 3, is real loss to you. Price the full industry distribution, not the buyer's expected loss.

When Does an ILW Beat Indemnity Reinsurance?

An ILW beats indemnity reinsurance when cost, speed or capacity matter more than precise loss matching, and when the buyer's losses track the index closely. Indemnity cover wins when the buyer's book is concentrated or unlike the market.

Many buyers use both. Indemnity cover protects the core, and ILWs add remote or opportunistic capacity where the price gap is wide.

Which ILW Mistakes Are Most Expensive?

Six mistakes cause most ILW disappointment. Each one is avoidable at placement.

How Should Buyers Evaluate an ILW?

Evaluate an ILW by modelling your own losses and the industry index together, event by event. The goal is to see where they diverge, not just their average relationship.

What Analysis Should You Run?

Which Questions Should You Ask?

• Which index provider, territory and peril definitions apply, and do they match our exposure?
• How long is the reporting period, and can it be extended if the index is still developing?
• Is the cover binary or pro rata, and how close is the trigger to where losses cluster?
• Is there a UNL trigger, and how will we evidence our loss?
• Is the seller collateralised, and when is collateral released?

For a wider view of how ILWs sit within outwards protection for reinsurers, see our guide to retrocession and reinsuring the reinsurers.

How Do ILWs Affect Capital and Accounting?

The capital and accounting treatment of an ILW depends mainly on whether it contains an indemnity trigger and how much basis risk it leaves. Confirm treatment before binding, not after the first event.

Solvency II

Under Article 210 of the Solvency II Delegated Regulation, a risk-mitigation technique should not result in material basis risk unless that risk is reflected in the SCR calculation. Basis risk is material where it would lead to a misstatement of the risk-mitigating effect that could influence decisions.

For ILWs, that means the cedent must assess and evidence the basis risk before taking capital credit. Internal model firms can model it directly, while standard formula firms should discuss the treatment with their supervisor.

IFRS 17 and IFRS 9

A dual-trigger ILW that requires the buyer to suffer a loss generally transfers insurance risk and falls within IFRS 17 as reinsurance held. An index-only ILW does not compensate the buyer for its own loss, so it is generally treated as a derivative under IFRS 9 and measured at fair value.

The classification affects how results flow through profit or loss. It should be documented contract by contract.

How Do ILWs Fit With Cat Bonds and Parametric Cover?

ILWs sit between indemnity reinsurance and parametric cover. Indemnity pays on your loss, an ILW pays on the industry's loss, and parametric cover pays on a physical measure such as wind speed or ground shaking.

Industry-index triggers are also common in catastrophe bonds, where the same basis-risk trade-off applies. Our guide on how cat bonds went mainstream covers that market, and our piece on parametric cat insurance for reinsurers covers physical triggers.

What Does the Market Look Like for 2027?

ILW capacity is supplied largely by reinsurers and ILS investors, and it tends to expand when third-party capital is plentiful. With capacity returning after the 2023 reset, buyers have more room to compare ILW and indemnity pricing.

In a softening market, the price gap between ILWs and indemnity cover can narrow. When it does, the basis risk in an ILW becomes harder to justify, and buyers should recheck the trade-off at each renewal.

Checklist for Heads of Retro and Outwards Reinsurance

Use this checklist before you buy or renew an industry loss warranty.

• Own loss and industry loss have been modelled together, event by event
• Loss share stability has been tested by region and peril
• The index provider, territory and peril definitions match the exposure
• Binary and pro rata forms have been compared on the same events
• The reporting period allows for index development to a final estimate
• A UNL trigger is included where reinsurance treatment is required
• Solvency II and IFRS treatment have been confirmed in writing
• ILW recoveries and index updates are tracked alongside indemnity layers

A centralised reinsurance treaty management platform can hold ILW terms beside indemnity treaties. That keeps triggers, limits and expected recoveries visible in one place when an event unfolds.

Key Terms

Industry loss warranty (ILW): A contract that pays when industry insured losses from an event exceed an agreed trigger, usually with an ultimate net loss condition.

Industry loss trigger: The industry-wide insured loss level, as reported by a named index provider, at which the ILW pays.

Ultimate net loss (UNL) trigger: A condition requiring the buyer to suffer its own net loss from the event, which usually also caps the recovery.

Basis risk: The mismatch between the buyer's own loss and the payout under an index-based cover.

Binary ILW: An ILW that pays its full limit once the industry trigger is reached.

Pro rata ILW: An ILW that pays progressively as the industry loss moves between attachment and exhaustion points.

PCS (Property Claim Services): A Verisk unit that designates catastrophe events and estimates industry insured losses, used widely as an ILW index.

PERILS AG: A Zurich-based provider of industry exposure and loss data, whose index values are used in ILS, ILW and derivative triggers.

Sources

• PCS Catastrophe Loss Indexes Worldwide, Verisk
• PERILS Industry Loss Index Service
• Commission Delegated Regulation (EU) 2015/35 (Solvency II)
• IFRS 9 Financial Instruments, IFRS Foundation