Aon's 20th ILS report: record issuance, unanswered sidecar question

Aon's 20th annual insurance-linked securities report, published in August 2026, argues that ILS now works as foundational reinsurance capital across property and casualty lines, a claim the numbers in the report make harder to dismiss than they would have a decade ago. Alternative capital reached a record $144.5 billion, growing roughly 8.3 percent annually over the past five years, while cat bond issuance over the twelve months through June 30 hit $24.9 billion, the highest twelve-month figure on record and 15 percent above the previous peak of $21.8 billion. Outstanding cat bond volume climbed to a record $63.4 billion, up 17 percent from a year earlier, which Aon says reflects an estimated 11.6 percent compound annual growth rate over the past decade.

The report's sidecar numbers carry the more consequential claim. Aon estimates outstanding sidecar capital at $23 billion across property and casualty lines, roughly 50 percent higher than at year-end 2024, with growth driven by strong margins and an expanding set of casualty-focused sidecars. Those asset-intensive structures typically carry casualty lines or whole-account portfolios, which takes the market beyond the event-driven perils it was built on. The sponsorship base is broadening with the product menu: a record 78 sponsoring entities accessed the cat bond market during the period, including 16 first-time issuers, with insurers at 65 percent, reinsurers at 17 percent, governments at 16 percent and corporate entities at 1.5 percent. The report also notes expansion beyond traditional North American peak perils to wildfire, European flood and convective storm, sovereign disaster relief and other specialized risks.

Richard Pennay, chief executive of Aon Securities, calls the twelve months a milestone in the market's evolution, with ILS providing clients a durable source of capital while continuing to attract investor interest. The return data backs the enthusiasm: catastrophe bonds produced 12.5 percent over the period, according to the Aon Securities Catastrophe Bond Total Return Index, with coupon income the key driver of returns and reinvestment.

That 12.5 percent is a catastrophe bond return, the figure the report's public summary holds up, and it belongs to the market's oldest products. The public performance figures do not include a comparable measure for casualty sidecars, so the most visible return data has nothing to say about the structures that drove half the year's expansion. The omission matters because sidecar capital growth is a different underwriting proposition from a hurricane or earthquake bond. Aon's report links the sidecar build-out to strong margins in casualty lines. As this publication has argued, ILS expansion beyond natural catastrophe is really capital-standards expansion, and the product build-out is running ahead of the balance-sheet experience that would tell investors whether casualty sidecar risk is being paid for correctly.

The records themselves are real: $144.5 billion in alternative capital, $63.4 billion in outstanding cat bonds and 16 first-time issuers are not the marks of a marginal market. Aon is right to call ILS foundational in the sense that the data shows a market treating collateralized capital as a permanent part of the risk-transfer stack. What the foundation is built on is less settled: cat bond issuance at $24.9 billion and a 12.5 percent return are the headline achievements of the past twelve months, while the sidecar expansion is the one that changes the market's shape, and the report offers no full-cycle track record for those structures and no public index by which to measure them.

The renewals to watch are the ones where whole-account sidecar capacity meets its first adverse development, and the price of the next deployment after it surfaces. The 21st edition will need to answer that question: if the casualty sidecar build-out prices through a loss year, the foundational label will be earned; if it has been riding the cat-bond bull market, the first sign will be a sidecar renewal repriced after the reserves develop rather than an index return.