How do you make better investment decisions under uncertainty?

Core article 1 in Architecture of Wealth

Meta description: A practical framework for assessing investment decisions by their process, assumptions and consequences—not solely by their outcome.

A share price rises shortly after you buy it. Was it a good decision?

It depends.

Perhaps you analysed the company carefully, considered alternative explanations and deliberately limited the size of the position. But perhaps you bought into a compelling story, were fortunate enough to benefit from an unexpected takeover bid and later reclassified luck as insight.

The reverse also occurs. A carefully considered decision can produce a loss—not because the process was flawed, but because investing takes place in a world where chance, behaviour and unexpected events continue to matter.

That leads to one of the most difficult lessons for any investor:

A good outcome does not prove that the decision was good. A poor outcome does not automatically prove the opposite.

If you judge decisions solely by their results, you may learn precisely the wrong lesson.

Why this matters to you

A weak decision process costs more than return. It can also erode time, flexibility and confidence. If you are still building wealth, you can spend years pursuing a persuasive but unsound idea. If you already have wealth, a single oversized position can damage earlier progress. And with substantial or complex wealth, separate decisions may unknowingly accumulate the same underlying risk.

This article will not help you predict which investment will win. It will help you examine whether a decision is defensible before the outcome is known—and whether your plan can survive being wrong.

Investing means deciding with incomplete information

For many financial choices, certainty is unavailable when action is required. You know the current price, the available figures and other people’s expectations. You do not know every future competitor, policy change, innovation or behavioural response.

More information solves this only in part.

Information can reduce uncertainty. It cannot remove it. In fact, if you search long enough, you will usually find arguments both for and against the same investment. A new trap then appears: research ceases to be a tool for making a decision and becomes a way to postpone it or confirm an existing belief.

The professional question is therefore not:

How do I achieve certainty?

It is:

How do I make a defensible decision while certainty is unavailable?

Separate three kinds of uncertainty

Not every unknown deserves the same amount of research.

1. What you can know

Balance-sheet ratios, costs, valuation, diversification, contractual terms and a company’s financial position are examples. Here, carelessness is avoidable. Gathering facts has value.

2. What you can estimate

Future earnings growth, inflation, interest rates and market growth cannot be known exactly, but scenarios and ranges can be used. An estimate is not a fact. It becomes useful when the assumptions beneath it are visible.

3. What remains fundamentally uncertain

A geopolitical shock, an unexpected technological breakthrough or the precise response of millions of market participants cannot be predicted reliably. Another decimal place will not help. The portfolio must be designed so that it does not depend on one outcome.

Many mistakes arise when investors confuse these categories. They treat an estimate as a fact and fundamental uncertainty as a lack of research.

Start with the decision, not the investment

“Is this stock attractive?” is rarely the complete question.

A better formulation might be:

Does a position in this company, at this price and of this size, fit my objective, horizon and capacity for loss?

Four separate decisions now become visible:

what you buy;
the price you pay;
how much you buy;
the conditions under which you hold, add or sell.

A good analysis can still produce a poor portfolio if the position is too large. Conversely, an uncertain investment can be defensible when the position is small and the potential damage is limited.

The question am I right? is too narrow. The better question is: what happens if I am wrong?

The same error, different consequences

The meaning of an investment decision depends on the circumstances in which it is made.

You are still building wealth

A poor choice may look limited in euros, but it can consume valuable years of accumulation. This is precisely the phase in which seeking fast returns, following popular ideas or mistaking a temporarily good outcome for proven skill can be most tempting.

You have wealth that needs direction

The challenge shifts from finding money to invest to assessing choices as a whole. An individual investment may be attractive but still resemble risks that are already present elsewhere in the portfolio.

Your wealth is substantial or complex

The danger is no longer confined to a single poor investment. Risk can accumulate across a business, property, securities, currencies and future obligations. The quality of decision-making then becomes a governance question as well: who decides, on what basis and within which limits?

The sums differ. The discipline remains the same: make the assumption visible, examine what could disprove it and limit the damage if the future unfolds differently.

A seven-step decision framework

Step 1 — Define the purpose

What must this decision contribute?

Long-term growth? Income? Protection against inflation? Diversification away from an existing business? Or mainly the feeling that idle cash “ought to be doing something”?

That last reason sounds less professional, but it is common. The urge to act disguises itself easily as strategy.

An investment can be attractive and still be unsuitable for the role assigned to the capital.

Step 2 — Make the central assumption visible

Every decision rests on an expectation. For example:

profitability will remain above average;
debt remains manageable;
the market underestimates the company;
cash flow remains sufficient;
the current headwind is temporary.

Write the central assumption in a single sentence. If that is impossible, the story is probably moving in too many directions at once.

Then ask: what must happen for this assumption to prove correct?

Step 3 — Actively look for disconfirming evidence

Investors naturally collect information that supports their initial view. It feels like research, but it is often confirmation.

Reverse the process:

Why might the market be right after all?
Which competitor benefits from a different outcome?
What development would undermine my analysis?
What does a critical outsider see that I would rather not see?
Would I find the same arguments convincing if I did not already own the investment?

A belief does not become stronger because you ignore objections. It becomes stronger when it survives serious ones.

Step 4 — Use ranges, not point forecasts

An expected return of precisely 7.3 per cent looks rigorous. Usually the precision says more about the model than about the future.

Use several scenarios instead:

what happens in a favourable development?
what is a plausible base case?
what happens when margins, growth or valuation disappoint?

The purpose is not to make three new predictions. It is to discover which assumptions dominate the outcome and how much space exists between disappointment and permanent damage.

Step 5 — Examine the downside consequence

Risk is not only the probability that something goes wrong. It is also the damage when it does.

Ask questions such as:

Can I bear the loss financially?
Does this affect one position or several parts at once?
Could I be forced to sell at an unfavourable moment?
Is the decision reversible?
How much capacity for recovery remains?

A bridge is not designed only for an average Tuesday. Neither is a portfolio.

Step 6 — Let uncertainty determine position size

Investors spend a great deal of time deciding what to buy and remarkably little deciding how much to buy.

Yet position size is often where conviction becomes vulnerability. The greater the uncertainty and the more serious the potential consequences, the less logical a large position becomes.

That sounds simple. In practice, the opposite often happens. An investor becomes more convinced, reads more supporting information and increases the position. The analysis then becomes not only a judgement about the investment but also a defence of the earlier decision.

A margin of safety is therefore not found only in the purchase price. It is also found in the size of your conviction.

Step 7 — Decide in advance when to review

Without agreed review points, you respond to whatever demands attention most loudly: falling prices, news reports and other people’s conviction.

Record in advance:

which new fact would weaken the original assumption;
when the decision will be reviewed;
which change is a reason to do nothing;
which change genuinely requires action.

A price decline is not, by itself, proof that the analysis was wrong. A rise does not prove it was right either.

When is information sufficient?

Complete information does not exist. Yet you can decide both too early and too late.

A practical boundary is reached when further research is unlikely to change the choice. Ask yourself three questions:

What information is still missing?
Can that information genuinely change my decision?
What is the cost of waiting?

Waiting is not free. An opportunity may disappear, but more importantly, delay can itself be a choice without being treated as one. Holding cash, not selling or not taking a position also has consequences.

This does not mean faster is always better. It means delay needs an explicit reason too.

Keep a decision journal

Memory is a friendly editor. After a good outcome, we mainly remember the arguments that proved right. After a poor outcome, we like to emphasise that nobody could have foreseen it.

A short decision journal makes learning more honest. Before the decision, record:

the purpose;
the main assumption;
the strongest counterarguments;
the expected range of outcomes;
the maximum acceptable damage;
the reason for the position size;
the timing and conditions for review.

Later, assess the process before the outcome.

Could you have known the relevant information? Did you take counterevidence seriously? Was the size appropriate for the uncertainty? Did you follow your own rules?

This prevents profit from automatically becoming confidence and loss from automatically becoming a new strategy.

Four biases to keep in view

Outcome bias

You judge a decision after the event by its profit or loss and forget how much luck or misfortune influenced the result.

Confirmation bias

You look for information that supports your existing belief and apply a higher standard to counterevidence.

Recency bias

What happened recently feels more representative of the future than it deserves to be.

Action bias

Acting feels decisive. Doing nothing feels passive, even when waiting is part of a pre-agreed process.

Experience does not eliminate these biases. It can even disguise them more effectively. After many years in the profession, you have more stories available to explain almost any decision after the event.

A sound process is not a guarantee

Even the best method cannot prevent losses. That is not the standard by which it should be judged.

A sound process does something else:

it makes assumptions visible;
it limits avoidable errors;
it links conviction to position size;
it protects against decisions made under pressure;
it makes genuine learning possible.

Its value often becomes clearest when the outcome disappoints.

The final question before making an investment is therefore not only:

Why do I think this could work out well?

But also:

Which mistake can I afford without disrupting the entire plan?

That is not a lack of conviction. It is a professional response to the fact that the future has no obligation to follow your analysis.

The essence

The quality of a decision cannot be inferred solely from its outcome.
Make the underlying assumption visible in advance, together with the evidence that would disprove it.
Let the uncertainty that remains—not only your conviction—determine position size.
Decide in advance when to review, so that market stress does not write your rules in real time.

A good investor does not try to be right all the time. A good investor ensures that being wrong does not damage the entire structure.

From a decision to a wealth architecture

One carefully made decision does not create a coherent portfolio. Every choice relates to your objectives, other investments, available time and financial capacity.

The e-book Architecture of Wealth develops this broader framework. It is not a collection of investment tips, but a method for making separate decisions part of a manageable whole. This article helps you assess one decision more effectively; the e-book shows how decisions, risk, behaviour and portfolio design come together in one architecture.

Sources and further exploration

Baron, J. & Hershey, J.C. (1988), Outcome bias in decision evaluation, Journal of Personality and Social Psychology.
Dutch Authority for the Financial Markets, Important insights on self-directed investors (source in Dutch).
Dutch Authority for the Financial Markets, Investment behaviour among execution-only investors (source in Dutch).

This article contains general information and educational insights. It does not take your personal financial situation, objectives or risk tolerance into account and does not constitute individual investment advice. Investing involves risk. You may lose some or all of your investment.