Definition
Risk sharing is the structural property of a claim that specifies who bears the longevity risk associated with the claim, with four possible values: none, pooled, transferred, or hybrid.
Why it matters
The risk-sharing property is the foundational structural fact about any lifetime income arrangement. It determines whether mortality credits exist at all, who captures them when they do, and what it costs to access them. Without naming it explicitly, it is impossible to compare arrangements that handle longevity risk in fundamentally different ways.
How it works
Risk sharing takes one of four values. None — the individual bears all longevity risk alone, with no pool and no transfer; this is the structure of solo drawdown. Pooled — longevity risk is shared among members through mortality credits, with surviving members receiving the share that died members would have received; this is the structure of a tontine or direct pool. Transferred — longevity risk is shifted to an insurer in exchange for a fee, with the insurer bearing the risk and pricing the contract to absorb it; this is the structure of a SPIA, a DIA, or a fixed indexed annuity with an income rider. Hybrid — some risk is pooled, some retained, some transferred; this is the structure of a variable annuity with a guaranteed lifetime withdrawal benefit, where the underlying account exposes the individual to investment risk while the rider transfers a portion of longevity risk to the insurer.
In practice
When you evaluate a lifetime income arrangement, the first question to ask is which of the four risk-sharing values applies to it. The answer determines what category of arrangement you are evaluating and what the relevant comparisons are. A SPIA and a direct pool are not really competitors — they are different risk-sharing categories, and choosing between them is choosing how you want longevity risk to be borne, not just choosing a price. A professional who cannot name the risk-sharing value of an arrangement they are recommending has not characterized the arrangement structurally. For a plan fiduciary, requiring every proposed in-plan lifetime income option to be characterized by its risk-sharing value is the first step in any defensible evaluation process.
In the Longevity Standard Framework
Risk sharing is one of four claim properties in the Longevity Standard framework. The four properties — risk sharing, adjustment mechanism, liquidity, cost structure — together characterize any lifetime income arrangement structurally. Risk sharing and adjustment mechanism together describe how the claim works mechanically — the structural pair of the four-property framework. Risk sharing is the foundational property because it determines whether a mortality credit exists, who captures it, and what it costs to access; the other three properties become operative only after the risk-sharing value is fixed. Within the cost-of-income framework, transferred-risk arrangements are evaluated against the frictionless pool benchmark with the insurer load measuring the cost of the transfer; pooled arrangements are evaluated against the same benchmark with explicit fees or governance-determined costs measuring the cost of access; solo arrangements (risk sharing — none) constitute the baseline against which all pooled and transferred arrangements are measured.
Related terms
- Adjustment mechanism
- Liquidity
- Cost structure
- Mortality credits
- Frictionless pool
- Solo drawdown
- Insurer load
- Longevity risk