Investing Basics
The horizon is the variable that constrains everything else
How long money can be left alone determines what can sensibly be done with it, more decisively than temperament, expertise or the amount involved.
By Varun Krishnan3 min read
One input does most of the constraining
A great deal of energy in personal finance goes into questions of temperament, product selection and market conditions. Those matter at the margins. The variable that eliminates most of the options before any of them are considered is simply when the money will be needed, and it is the one that requires no expertise to establish.
The logic is not complicated. Anything that can fall in value over a period is unsuitable for money required at the end of that period, because the fall and the requirement can coincide. Anything that cannot fall in value generally does not keep pace with rising prices over long periods. The horizon selects between these constraints.
What makes it powerful is that it is a fact about your own plans rather than a prediction about anything external. You cannot know what markets will do. You can usually say, within reason, whether a sum is needed next spring or in twenty years.
A short horizon eliminates almost everything
Money needed within a couple of years has a narrow set of sensible homes, and the reason is asymmetry. A rise of ten per cent between now and the date is pleasant but not necessary. A fall of thirty per cent means the thing the money was for does not happen. The upside and downside are not symmetrical in consequence even when they are in probability.
This is why deposits, savings accounts and similar arrangements exist and why their unimpressive returns are not the point. They are being used for their reliability of amount, which is the property the horizon demands. Paying for that property with a lower return is a purchase, not a failure.
The mistake in the other direction is common enough to be worth naming: money for a near-term purpose placed somewhere that can move, on the reasoning that the return is better. The return is better on average and irrelevant if the specific two years in question go the wrong way.
A long horizon changes what volatility means
Over long periods, movement matters less because there is time for it to reverse and because nothing forces a sale at the bottom. What matters more is the cumulative effect of growth against the cumulative effect of rising prices, and that comparison favours arrangements that can move over arrangements that cannot.
The mechanism is compounding, applied to a real rather than nominal figure. A small annual difference in growth above inflation, extended across decades, produces a large difference in purchasing power. Across five years it produces very little, which is precisely why the horizon changes the answer rather than merely softening it.
This does not mean a long horizon makes risk disappear. It means the balance between the different meanings of risk shifts, and the one that dominates a long period is not the one that dominates a short one.
The horizon has to be honest, not aspirational
The stated horizon is only useful if it survives contact with the household’s actual life. Money nominally set aside for twenty years, held by a household with no buffer and unstable income, has a real horizon of however long it is until something goes wrong. That is when it will be reached for, whatever the intention was.
This is the practical argument for a cash buffer sitting in front of anything long-term. Its function is not only to absorb shocks; it is to protect the horizon of everything behind it, by making sure the long-term money is not the thing reached for in an emergency.
A related honesty problem is the horizon that shortens as it approaches. Money for a purpose ten years away is money for a purpose two years away eventually, and the arrangement appropriate at the start is not the one appropriate near the end. The horizon is a moving quantity, not a fixed label.
Different pots, different horizons, no contradiction
It follows that a household can quite reasonably hold money in arrangements that look inconsistent with each other. Cash for near-term needs, something else entirely for a purpose decades away. There is no contradiction, because the two pots are answering different questions.
What is genuinely inconsistent is a single undifferentiated pool being used for every purpose, which forces one arrangement to serve horizons it cannot serve simultaneously. Separating money by when it is needed is the step that makes each subsequent decision tractable.
How any of this applies depends on income stability, obligations, local products and what the money is actually for. This is a description of why the horizon constrains the choice, not a recommendation about any arrangement, and anything substantial is worth taking to a regulated adviser.
Common questions
What counts as a long horizon?
There is no clean threshold and any specific number would be arbitrary, but the useful principle is that a horizon is long enough when a substantial fall could occur and still have time to reverse before the money is needed. That is a judgement about the specific purpose rather than a fixed number of years.
What if I do not know when I will need the money?
Uncertainty about the date is itself information, and it generally argues for treating the horizon as shorter than the optimistic estimate. Holding a separate buffer for the unpredictable needs allows the rest to be treated as genuinely long-term, which is why the two pots work better than one.
Should the arrangement change as the date approaches?
The horizon shortens as the date approaches, so the constraints that applied at the start no longer apply near the end. Many long-term plans include some form of gradual shift for that reason. How and whether to do this for a particular goal is exactly the sort of question worth putting to a regulated adviser.
Varun writes the explanatory pieces on spending, saving, debt and would rather show the working than assert the conclusion.
