Glide paths: reducing risk as the horizon shortens

What a glide path actually is

A glide path is a written rule that says how the composition of a pool of money changes as a target date approaches. It usually reduces the proportion held in volatile, growth-oriented assets and increases the proportion held in stable, income-oriented or cash-like assets as the date gets closer.

The name comes from aviation. An aircraft descends along a defined path rather than dropping suddenly at the last moment. The analogy is apt in one important respect: the descent is planned in advance, not improvised in response to conditions on the day.

That advance planning is the entire point. Almost everyone reduces risk eventually. The question is whether they do it according to a rule written when they were calm, or according to their emotions during a market fall. A glide path is a commitment device first and an optimisation second.

Life-cycle and target-date structures built on this idea are a standard feature of defined contribution pension systems in many countries, where the default investment option shifts allocation automatically as the member ages Source^source.

A glide path reduces exposure to one kind of risk by accepting more of another. It does not reduce total risk. Moving from growth assets to cash-like assets exchanges volatility risk for the risk that your money loses purchasing power over a long retirement. Both risks are real.

The problem it is designed to solve

If long-horizon returns were the only thing that mattered, there would be no reason to de-risk. You would hold the highest-expected-return mix forever and accept the swings.

The reason that fails is a phenomenon called **sequence of returns risk**. It is worth understanding precisely, because it is the load-bearing argument for the entire concept.

Why order stops mattering and then starts again

Suppose you invest a lump sum and never add to it or take from it. Over ten years you experience returns of +20, -15, +8, +30, -10, +12, +5, -20, +25 and +6 percent. Now reshuffle those same ten returns into any order you like. The final value is identical. Multiplication is commutative. The order of returns is irrelevant when there are no cash flows.

Now add cash flows and the property vanishes.

Consider two people, each retiring with 1,000,000 and each withdrawing 50,000 a year, adjusted upward for inflation. Both experience exactly the same set of annual returns over twenty years — same average, same volatility, same everything. The only difference is the order.

Person A gets the bad years first. In year one the portfolio falls 25 percent to 750,000, and they withdraw 50,000, leaving 700,000. The withdrawal is now 7.1 percent of the remaining balance rather than 5 percent. In year two it falls again. By the time the good years arrive, they are compounding a much smaller base, and the withdrawals have permanently removed units that can never participate in the recovery.

Person B gets the good years first. Their portfolio grows to 1,300,000 before the bad years arrive, and the same 50,000 withdrawal is a smaller share of a larger base. When the fall comes, it comes from a higher level and against a bigger cushion.

Same returns. Same withdrawals. Radically different outcomes, and in extreme versions of this comparison one portfolio survives the full period comfortably while the other is exhausted.

The mechanism is straightforward once seen. Withdrawing from a fallen portfolio locks in the loss for the withdrawn portion. You cannot un-sell those units. During accumulation, the same logic runs in reverse and works in your favour — contributing during a fall buys more units at lower prices, which is why a market decline early in a long saving life is not obviously bad news.

This asymmetry is why the risk profile of a portfolio should not be constant. Early on, when you are adding money and have decades of recovery time, volatility is tolerable and arguably useful. Late on, when you are drawing money and have no time to recover, the same volatility is dangerous. The glide path is the bridge between those two states.

The vulnerability window

Sequence risk is not uniformly distributed across a lifetime. It concentrates in a window of roughly the last several years before the target date and the first several years after it. That is when the portfolio is at its largest — so a given percentage fall is the largest absolute loss it will ever suffer — and when the remaining time to recover is shortest.

A 30 percent fall on a portfolio of 100,000 at age 30 costs 30,000 and has thirty years to recover. The same 30 percent fall on 1,500,000 at age 60 costs 450,000 and has to recover while being drawn down. It is the same percentage and an entirely different event.

If you take one practical idea from this article, make it this: the years immediately around your target date deserve more attention than any other period, and they are exactly the period most plans treat as an afterthought.

Calendar glide paths versus funding glide paths

The standard glide path is **calendar-based**. It de-risks according to how many years remain until a fixed date. Target-date funds work this way, and the old rule of thumb — hold a percentage in bonds roughly equal to your age — is a crude calendar glide path.

The alternative is **funding-based**. It de-risks according to how close you are to having enough, regardless of the date.

The difference matters more than it sounds. Consider two people, both aged 55, both targeting retirement at 65.

Person C has already accumulated enough to fund their planned spending, assuming modest real returns. Their problem is no longer growth, it is preservation. Additional risk buys them a larger surplus they do not need, at the cost of a chance of falling below adequacy. For them, de-risking early is rational — they have won the game and should stop playing it.

Person D is significantly short of what they need. A calendar glide path would de-risk them on schedule, which mechanically locks in the shortfall. Their situation calls for a different conversation entirely: extending the horizon, increasing contributions, reducing the target, or accepting more risk with clear eyes about what a bad sequence would mean. Automatically de-risking Person D does not make them safe. It makes their shortfall certain rather than probable.

A funding-based approach ties the de-risking trigger to a funded ratio — roughly, the value of your assets divided by the present value of what you need them to deliver. When that ratio crosses comfortably above 1, you shift risk down. When it sits well below 1, mechanical de-risking is not the answer to your problem.

Most real plans should be a hybrid: calendar-based as the default, with funding-based overrides in both directions.

Four questions before you de-risk anything

Before applying any glide path to any pool of money, work through these.

1. **When is the money actually needed — as a lump or as a flow?** A deposit for a property purchase in three years is a single date with a hard edge. Retirement income is a flow spread over decades. The first calls for genuine de-risking to near-certainty. The second calls for partial de-risking, because a portion of that money will not be spent for twenty-five years and still has a long horizon of its own.
2. **What happens if the target is missed by 20 percent?** If the answer is "I delay by two years", the goal is flexible and can tolerate more risk. If the answer is "the transaction fails and I lose my deposit", it cannot. Flexibility of the goal is as important as the length of the horizon.
3. **Is there other income that covers the essentials?** If a state pension, an annuity, rental income or a spouse's earnings cover your non-negotiable costs, the portfolio is funding discretionary spending and can carry more volatility. If the portfolio is the only source of essential spending, it cannot.
4. **What is the cost of being wrong in each direction?** De-risking too early costs you foregone growth over a long retirement, which shows up as a shortfall in your late seventies. De-risking too late costs you a large loss at the worst possible moment. These are different failure modes with different timing and different reversibility. The late failure is far harder to fix, which is the honest argument for erring slightly early.

Three buckets, instead of one number

The single-percentage view — "I am 60, so I should be 40 percent in growth assets" — collapses a rich problem into one number. A more useful reframing splits money by when it will be spent.

**Bucket one: the next two to three years of spending.** Held in cash or cash-like instruments. Its job is not to grow. Its job is to guarantee that you never have to sell a fallen asset to buy groceries. This bucket is what actually neutralises sequence risk, because it breaks the link between market conditions and forced selling.

**Bucket two: years three to roughly ten.** Held in more stable, income-oriented assets. Its job is to refill bucket one, and to be reasonably reliable over a medium horizon without being eroded by inflation as fast as pure cash.

**Bucket three: year ten onward.** Held in growth-oriented assets. Money that will not be spent for a decade or more still has a decade or more of horizon. Treating it as short-term money because of the owner's age is a category error — the owner's age is not the horizon, the money's spending date is.

Note that the buckets imply an overall allocation, so this is not a contradiction of the percentage view. It is a different route to it, and it produces a much more defensible answer, because each bucket's risk level is justified by a specific spending date rather than by a birthday. It also gives you a rule for what to sell during a downturn: refill from bucket two, leave bucket three alone, and let time do its work.

The mechanics require discipline. You must actually refill the buckets, which means selling growth assets after good years to top up the stable ones. That is rebalancing under another name, and the fact that it feels wrong — selling what has done well — is precisely why it needs to be written down in advance.

Where the standard assumptions break

Glide paths rest on assumptions that are worth stating plainly, because when they fail, they fail together.

**The assumption that stable assets are stable.** Bonds are less volatile than equities in most environments, but they are not risk-free. They carry interest rate risk, credit risk and inflation risk. A long-duration bond can fall substantially when rates rise. Investors who thought of their bond allocation as the safe portion have periodically discovered otherwise.

**The assumption that stable and growth assets move differently.** Much of the appeal of shifting from equities to bonds rests on the idea that they offset each other. That relationship is not a law of nature. The correlation between bonds and equities has changed sign across historical regimes, and periods where both fell together have occurred Source^source. A glide path built on the assumption of reliable negative correlation is more fragile than it appears.

**The assumption of a single retirement date.** Many people phase out of work gradually, take contract work, or return to employment. A cliff-edge glide path targeting one date does not describe that reality well.

**The assumption that the portfolio is the whole picture.** In the UAE, an employee may be entitled to an end-of-service benefit or participate in an alternative savings scheme under arrangements overseen by the Ministry of Human Resources and Emiratisation Source^source. Whatever form such an entitlement takes, it is a separate pool with its own characteristics and timing, and it should be counted before deciding how much risk the personal portfolio needs to carry. The same applies to property, business interests and any home-country pension. A glide path applied to one account while ignoring three others is optimising a fragment.

**The assumption that lower volatility means lower risk of ruin.** For a thirty-year retirement, a portfolio held entirely in cash-like assets has near-zero volatility and a meaningful probability of running out, because inflation compounds against it every year. De-risking past a certain point converts a visible risk into an invisible one. The visible one is easier to bear emotionally and the invisible one is more likely to be fatal.

Building a rule you will actually follow

A glide path is only useful if it survives contact with a bad year. Some practical constraints that make that more likely:

• **Write it down before you need it.** Specify the target allocation at each stage, the trigger for each shift, and the tolerance band. A rule invented during a 25 percent decline is not a rule.
• **Use bands, not points.** "Rebalance when growth assets drift more than 5 percentage points from target" is executable. "Maintain exactly 60 percent" generates constant trading and costs.
• **Move gradually.** Shifting a large allocation in one step on one date introduces its own timing risk. Annual or semi-annual increments spread that exposure.
• **Account for costs and constraints.** Transaction costs, spreads, minimum holding periods and any tax consequences in your jurisdiction all reduce the value of frequent adjustment. Simpler rules executed reliably beat elegant rules abandoned halfway.
• **Review the destination, not just the path.** The end-state allocation matters more than the shape of the curve. A path that lands at 30 percent growth assets and one that lands at 60 percent are fundamentally different plans regardless of how smoothly each descends.
• **Re-check the funded ratio periodically.** If you are far ahead of target, consider de-risking faster than schedule. If far behind, address the shortfall directly rather than pretending the glide path will fix it.

The honest summary

De-risking as a horizon shortens is not a rule of prudence handed down from nowhere. It is a specific response to a specific arithmetic problem: withdrawals from a fallen portfolio destroy capital permanently, and that problem is concentrated in a window around the target date.

Understand that and the design follows. Money needed soon should not be exposed to large swings. Money not needed for decades should not be treated as short-term simply because of the owner's age. The overall allocation is an output of those spending dates, not an input taken from a formula.

Nothing here says what allocation is right for you, because that depends on facts no article knows — your obligations, your other income, your currency needs, your tolerance for a falling balance and your capacity to keep working if things go badly. What it does say is that the decision deserves to be made deliberately and written down while you are calm, rather than discovered under pressure in the one year of your life when getting it wrong costs the most.