Alternative Reinsurance Capital Reaches $145 Billion as Liability Structures Expand

Alternative capital has grown into a significant source of reinsurance capacity, but its next stage depends on whether investors can get comfortable with risks that take years to resolve. The market now totals $145 billion, about 18% of global reinsurance capital, according to Richard Pennay, CEO of Aon Securities. Its growth is bringing more capacity to property programs and prompting insurers and investors to explore liability business, where uncertainty over claims, reserves and collateral duration is greater.

The pace has accelerated. Pennay said alternative capital expanded at an annual rate of about 6.5% over the past decade and about 13.5% over the past three years. That increase has helped move catastrophe bonds beyond their traditional role as protection against remote, severe events at the top of reinsurance towers. With capital inflows at record levels and spreads compressing, some bonds are attaching lower in those towers, said Terry McLean, president and CEO of SageSure.

Capacity and flexibility for cedents

Catastrophe bonds and other insurance-linked securities (ILS) have mostly covered low-frequency, high-severity exposures such as U.S. named windstorm and hurricanes. Niraj Patel, head of alternative capital for Axa XL, described that focus as a defining feature of the market. The appeal for insurers is that capital markets investors offer a source of capacity with different dynamics from traditional reinsurers, said Laurent Rousseau, CEO of global capital and advisory and head of international at Marsh Re.

That distinction can matter when traditional reinsurers limit their exposure to particular geographies. McLean said capital markets capacity can help buyers address those concentration constraints. It also gives cedents another source of funding, which can broaden the available capacity and diversify counterparty exposure. Patel said access to a deeper pool of capital can create pricing efficiencies, while Mitchell Rosenberg, co-head of global ILS at Howden Capital Markets & Advisory, characterized the main benefit as greater choice in how companies finance and transfer risk.

For cedents, that choice can add competitive pressure to reinsurance placements. Zach Breslin, capital markets leader for Lockton Re Capital Markets, said alternative capital lets buyers introduce competition into their programs. Rousseau said the market can absorb as much as 20% of reinsurance placements and renew that capacity, supporting efficient placement. In some parts of the United States, Aon has seen cedents place more than 25% of their overall reinsurance purchases through catastrophe bonds, Pennay said.

The share varies by buyer and program, but multi-year coverage is one reason some cedents have increased their use of catastrophe bonds. A bond can provide three or four years of protection, allowing a buyer to secure capacity and pricing across multiple renewal cycles. Breslin said that arrangement can reduce annual swings in both reinsurance costs and the capacity available to complete a program.

Multi-year protection can also change how much capacity a cedent needs to source at each renewal. When a catastrophe bond already covers a substantial portion of the reinsurance tower, the buyer only has to fill the remaining limit, said Jason Bolding, CEO of Gallagher Securities, Gallagher Re’s ILS division. That can make annual placements less exposed to changes in market conditions, though the bond’s value still depends on its terms and the risks it covers.

Liability brings a different set of demands

Property catastrophe remains the center of the alternative capital market, yet liability structures are attracting more attention. Pennay said that in the past 18 to 24 months, sidecars have expanded into whole-account and casualty-based arrangements. Bolding has also seen more cedents investigate alternative capital for casualty risks.

The move into liability is not a straightforward extension of catastrophe bond growth. Property catastrophe losses often arise from a defined event, while liability claims can develop over long periods and their ultimate cost may remain uncertain. A September report from A.M. Best said liability losses can take years to emerge and can be affected by changes in the legal and social environment. Those features make it harder for investors to estimate final losses and determine how long capital may need to remain committed.

That longer timeline brings reserving, duration and liquidity into the transaction’s economics. Patel said alternative capital for longer-tail lines requires investment modeling that accounts for collateral being held over an extended period. Rosenberg likewise pointed to greater reserving and liquidity considerations in casualty and other long-tail business. The challenge is to structure the risk so investors can assess the expected claims development and the period for which their capital may be tied up.

These constraints help explain why liability opportunities are developing through sidecars and other structures rather than simply replicating the property catastrophe bond market. The capacity is available, but the underwriting and investment assumptions must reflect a different pattern of loss emergence. For cedents, that makes the potential expansion meaningful while leaving execution dependent on how well each transaction handles uncertainty and time.

Collateral can remain tied up after losses

Alternative capital typically requires investors to post collateral in advance to support potential claims. When a major loss occurs, some of that collateral may remain unavailable beyond the contract term while estimates develop and claims are assessed. The result is known as trapped capital, a feature that can affect investors’ ability to redeploy funds and the attractiveness of future transactions.

The issue came into focus after hurricanes Harvey, Irma and Maria in 2017, when some investors could not redeploy capital until losses were resolved. Trapped collateral remained a concern after Hurricane Ian in late 2022, McLean said. Catastrophe bonds and collateralized reinsurance can include extension periods when loss estimates take months or years to settle, he said, adding that this creates friction not found in traditional unsecured treaties.

Bolding said the possibility of trapped capital is inherent in a market where losses take time to crystallize. The duration is difficult to know in advance, which makes the issue relevant to both property and casualty structures, though long-tail liability can add further timing uncertainty. Investors must weigh that possibility alongside the capacity and diversification benefits they provide.

Bond design can reduce some uncertainty in the claims process. Series 144A catastrophe bonds, which account for most of the market, use predetermined claims procedures intended to limit disputes, Breslin said. He said independent third parties administer a transparent recovery process. Those features can make the process clearer, but they do not eliminate the possibility that collateral will remain tied up while losses are evaluated.

The market’s continued growth will hinge on balancing the value of additional capacity with the costs and uncertainty that come with collateralized risk. Property catastrophe bonds are reaching further into reinsurance towers, while sidecars are opening paths into liability business. The next measure of progress will be whether structures can attract capital for longer-tail risks while giving cedents dependable coverage and investors a clearer view of how long their funds may be committed.