Why aging trajectory belongs in retirement planning
Two people can be born in the same year and face completely different futures. One has been physically active for three decades, sleeps well, and carries little chronic stress. The other has not. On paper — same age, same retirement-calculator inputs — they get the same plan. In reality, one will likely need that plan to fund a meaningfully longer life than the other. Yet retirement planning, almost everywhere, still starts from the wrong number: the year on a person's identity document.
Why averages aren't enough
Retirement planning, as practised by most providers, advisors, and individuals, is built on a small set of inputs: age, sex, current savings, planned contributions, target retirement age, and a payout choice. These are combined with population-level mortality and morbidity tables to produce a projection. The framework is venerable, transparent, and well understood — and it is also coarse.
The problem is that it treats a birth year as if it described a body. Two people who share one may have radically different physiological trajectories. One has been active for thirty years; the other has not. One sleeps well; the other has been chronically stressed. On average, the first tends to outlive the second — and a plan built on their shared birth year quietly under-serves one of them. The framework can't see the difference, because it was never designed to.
This isn't a rounding error. Longevity is the single most powerful variable in any retirement projection: how long the money must last determines almost everything else. Anchoring that variable to a population average, when the individual can differ from it by years in either direction, is the quiet flaw underneath an otherwise rigorous model.
A different anchor
The thesis is straightforward: retirement planning should start from how a person is actually aging, not from the year on their identity document. Modern smartphones already capture movement data that, properly analysed, yields a personalised aging trajectory — without a wearable, without manual logging. Combined with the standard financial inputs, that trajectory produces projections grounded in the individual rather than averaged across the population.
It is worth being precise about what this trajectory is and isn't. It is an estimate of the pace at which someone is aging, expressed with confidence intervals, validated against established biological-age markers. It is not a diagnosis, and it is not a fixed prophecy. A trajectory is an extrapolation of current behaviour — and behaviour changes. That is precisely the point: the signal is meant to inform action, not to foreclose it.
What changes in practice
When aging trajectory is on the table, several retirement decisions look different. A few examples.
If the data suggests someone is aging more slowly than their birth year implies, the plan may need to fund more years than a standard projection assumes — the most consequential adjustment in any retirement model. A longer expected horizon generally calls for a more conservative drawdown, so the money lasts; a shorter one may free up room to spend earlier, while it can be enjoyed. The same savings, two different shapes. And aging trajectory is a more personal signal than a population average for when care costs may arrive and how large a reserve to set aside against them. The same logic touches asset allocation, the cadence of tax-efficient withdrawals, and even the choice of retirement age.
A crucial point: none of these is a recommendation made by the product. Life & Health Metrics does not advise anyone to spend more, retire later, or hold a particular portfolio. It does one thing — it makes a single input, longevity, personal rather than averaged. What a person does with that input is a decision for them, and, where applicable, for their licensed financial advisor. A forecast is a lever, not a verdict: it informs the conversation; it does not replace the judgement.
For the full decision matrix and the methodology behind the trajectory, see the whitebook.