Risk, crashes and staying invested

Everything in the first three guides is straightforward. Own a slice of many businesses, in something cheap, and leave it alone. The mechanics are not the hard part.

The hard part is that at some point the number will drop a long way, it will keep dropping, and every instinct you have will tell you to make it stop. This guide is about that.

Volatility is not risk

These get used interchangeably and they are not the same thing at all.

Volatility is how much the price moves about. A volatile investment is one whose value swings widely, in both directions, often for no reason connected to the underlying business.

Risk is the chance of not having the money you needed, when you needed it — a permanent loss rather than a temporary one.

They overlap, but confusing them leads people to precisely the wrong conclusions. A volatile investment held for thirty years may carry little risk of a permanent loss. A stable-looking investment that quietly fails to keep up with the cost of living carries a very real risk of leaving you short, while never once appearing to have a bad day.

A price fall is not a loss. It becomes a loss at the moment you sell. Until then it is a quoted number that somebody else is willing to pay today, and the only thing that makes it permanent is your decision to accept it.

Why time horizon changes the entire question

The single most important thing about any money you invest is when you need it back.

Money you need next year has no time to recover from anything. If the market has a bad eighteen months and you have to sell into it, the temporary drop becomes your permanent result. Nothing about the long-term case helps you, because you were not there for the long term.

Money you do not need for twenty years is a completely different proposition. A bad year in the middle is something you read about later. You were not forced to act, so you were not harmed.

This is why every sensible answer to "is this a good investment" starts with a question about you rather than about the investment. The same fund can be entirely reasonable for one person and quite wrong for another, purely on the basis of when they need the money.

It also gives you a clean rule that requires no prediction: cash you may have to reach for shortly does not belong somewhere it can fall. That is not caution, it is matching the tool to the job.

Zoom out

Every chart is chaos on a one-day view. Watch a market minute by minute and it looks like a machine designed to frighten you, because on that timescale it is essentially noise — the aggregate mood of millions of people, most of whom are reacting to each other.

Stretch the same data over decades and the character changes completely. The frightening days are still in there. They have simply become too small to see.

Nothing about the underlying data changed between those two views. Only the window did. If you are investing for decades and panicking over an afternoon, one of those two timeframes is wrong — and it is not the decades.

The practical version of this is unglamorous: check less often. Someone who looks daily will see many more frightening days than someone who looks twice a year, and will have many more opportunities to do something regrettable. The information gained is close to zero. The chances to panic are considerable.

Falls are the entry price, not a malfunction

Investments in businesses return more than cash over long periods precisely because they are unpleasant to hold sometimes. If they went up smoothly and reliably, everyone would pile in and the extra return would be competed away. The discomfort is not a flaw in the arrangement. It is the arrangement.

This is the honest version of buy the dip, and it is worth being careful with, because the phrase has been thoroughly ruined by people using it to mean gambling. Red days are a sale nobody queues up for. Everyone insists they want to buy low, right up until things are actually low, at which point they discover an urgent need to sell instead.

What it does not mean is that a falling price is automatically a bargain, or that you should abandon a plan to chase a crash, or that borrowing to buy more is clever. A dip in a broad market you were going to buy anyway is a discount. An individual company falling because it is in trouble is just a company in trouble.

The shapes risk comes in

"Risky" is used as though it names one thing. It names at least six, and they behave differently enough that lumping them together leads to bad decisions.

• Market risk. Everything falls together because the world got gloomier. Diversifying across companies does not protect you from this; time and not being a forced seller do.
• Single-company risk. One business fails. This is the one diversification genuinely solves, and it is the reason not to hold one company.
• Inflation risk. Your money is intact and buys less. The risk of playing it too safe, and the one that never looks like a bad day.
• Currency risk. You hold assets priced in another currency and the exchange rate moves against you. Can help as easily as hurt, and mostly matters over shorter periods.
• Sequence risk. The order returns arrive in. Two people can experience identical average returns and end up in very different places if one met a bad stretch while drawing money out. This is why the years either side of needing the money are the ones that deserve attention.
• Liquidity risk. You cannot sell when you want to, or only at a bad price. Rare in mainstream funds, common in property and anything obscure.

Notice they pull in different directions. Reducing market risk by holding more cash increases inflation risk. There is no arrangement with none of them — only a choice about which you are best placed to absorb.

Lump sum or a bit at a time

Two questions come up more than any others, and this is the first: if you have a sum to invest, is it better to put it in at once or spread it over months?

The arithmetic and the psychology disagree, which is why the question persists.

• All at once puts your money to work immediately. Since markets rise more often than they fall over long periods, this wins more often than not — but not always, and it means the possibility of investing everything the week before a sharp drop.
• Spread over time guarantees you will not put everything in at the worst possible moment. It equally rules out putting it in at the best. What it buys is not a better expected outcome but a smaller chance of a start bad enough to make you quit.

If a bad first few months would make you abandon the plan entirely, spreading it out is not irrational, even though it is arithmetically the underdog. A slightly worse strategy you stick with beats a slightly better one you bail out of. That trade-off is the honest answer, and anyone giving you a confident one-word reply is skipping half of it.

Note this only applies to a lump sum you already have. Investing a portion of each month's income is not a strategy choice at all — it is simply what investing looks like when you are paid monthly.

Rebalancing, briefly

The second question. If you hold two things and one grows faster, it becomes a larger share of your total over time. A portfolio that started evenly split can drift into something considerably more concentrated without you doing anything.

Rebalancing means periodically selling a little of what grew and buying what did not, to return to your intended proportions. Its purpose is not to boost returns — it usually will not. Its purpose is to stop your risk quietly increasing while you are not looking, which is exactly what drift does.

It feels wrong every single time, because it means trimming the thing that is doing well to top up the thing that is not. That discomfort is the mechanism working: it is a rule that makes you sell high and buy low at moments when your instincts want the opposite.

Doing it once a year, or when something has drifted meaningfully off target, is plenty. Doing it constantly incurs costs for no benefit — and some funds handle it internally, in which case there is nothing for you to do at all.

Sizing something you can sleep through

Here is the most practical idea in this guide, and it is a question rather than a rule.

For anything you hold, ask: if this fell by half and stayed there for three years, what would I actually do?

If it would be uncomfortable but you would carry on, the size is right. If you would have to sell, or you would lie awake, the position is too big — regardless of how good the investment is. A position you can sleep through is a position you will still own when it matters, and still owning it is the entire point.

If a red candle is ruining your evening, the size is the problem, not the candle. That goes double for anything as violent as crypto, where halving is an ordinary event rather than a crisis.

Notice this requires no forecast. You are not predicting a fall. You are checking, in advance and while calm, that you have arranged things so a fall does not force your hand — because decisions made while frightened are reliably worse than decisions made in advance.

What a bad stretch actually feels like

Everything above is easy to agree with while things are calm. It is worth describing the experience honestly, because the gap between agreeing in principle and holding on in practice is where most damage happens.

A serious fall does not arrive as a single dramatic day you can brace for. It grinds. The value drops, recovers a little, and drops further. Each partial recovery invites you to believe the worst is over, and then it is not, which is considerably more corrosive than one sharp shock.

It also arrives with a full explanation attached. There will be a coherent, well-argued, entirely plausible account of why this time is genuinely different and why the usual reasoning no longer applies. Some of it will be from people far better informed than you. This is not a sign that something unprecedented is happening — it is what every fall has sounded like from the inside.

And it tends to coincide with other bad news, because the same conditions that hurt markets often hurt job security. That is precisely why the buffer discussed in the first guide is not a side note: it is the thing standing between a bad market and a forced sale.

None of that is an argument against investing. It is an argument for deciding, in advance and in writing, what you will do — because the version of you reading this calmly is a considerably better decision-maker than the version reading a red screen at midnight.

The plan has to survive you

A theoretically excellent strategy you abandon in month four is worse than a merely decent one you keep for thirty years. This is the point almost everything else in these guides has been quietly building towards.

Which means the honest test of any approach is not whether it is optimal. It is whether you will still be doing it when it is not working, because everything stops working sometimes.

• Write down why you own something, before you own it. Bad months are not the moment to be reconstructing your reasoning.
• Decide in advance what would genuinely change your mind — and make it something about the investment, not about the price.
• Automate what you can. A standing contribution keeps working on the days you would rather not look.
• Keep money you might need soon somewhere it cannot fall, so you are never a forced seller.

When it stops being investing

One last thing, because the line is easy to cross without noticing. A few honest signals that something has changed:

• You could not explain what the thing does, or where a return would come from, without using the word "potential".
• Your reason for owning it is that it has been going up.
• You are checking the price more than once a day, and the checking is doing something to your mood.
• The position is big enough that a large fall would change your plans rather than your feelings.
• You have borrowed to buy it, or you are using money earmarked for something real.

None of these are moral failings and none of them mean you will lose money. They are just a reasonably reliable indication that you have moved from owning a slice of businesses to taking a position on a price — a different activity with a different risk profile, which deserves to be sized accordingly and not confused with the boring thing this series describes.

None of that is clever, and that is rather the point. Clever is how people lose money interestingly.