The case for keeping it simple

Investment complexity is easy to acquire and difficult to justify, and the case for the simplest sufficient portfolio is stronger than it appears.

What complexity costs

Several things.

Higher charges, since specialised and active products cost more.

More transactions, each with a cost.

More decisions, each of which can be wrong.

More opportunities to interfere, which the behaviour gap evidence suggests is costly.

More time, which has value.

And more difficulty for anyone who has to take over the portfolio if you cannot manage it.

What it is supposed to add

The justifications.

Additional return, from active selection or factor exposure.

Additional diversification, from asset classes not in a simple portfolio.

Better risk-adjusted outcomes.

And access to opportunities unavailable simply.

Each is defensible in principle, and each requires evidence in the specific case rather than in general.

Why the evidence is weak

For most retail applications.

Active selection: the majority of active funds underperform after costs over long periods, and persistence is weak.

Factor exposure: premiums are real in the data and require holding through periods of underperformance longer than most investors tolerate.

Alternative asset classes: retail access is generally expensive and the diversification benefit is frequently overstated by valuation practices.

And optimisation on historical data produces portfolios that are confident about relationships that turn out to be unstable.

The simple sufficient portfolio

What it needs.

Global equity exposure for growth, broadly diversified across countries, sectors and company sizes.

High-quality bonds for stability, at a duration matched to the horizon and hedged to your currency.

Cash for short-term needs.

In proportions matched to horizon and capacity for loss.

Which is achievable with one to three funds at very low cost.

The maintenance argument

Frequently overlooked.

A portfolio must be maintained for decades, through periods of illness, distraction and eventually reduced capacity.

A complex portfolio requiring judgement is fragile to all of these.

And it is difficult for a partner or executor to understand if you cannot manage it.

Which is a genuine argument for simplicity that has nothing to do with returns, and which becomes more important with age.

Where complexity is justified

For balance.

Asset location across tax wrappers, which can improve after-tax returns meaningfully for people with substantial taxable holdings.

Specific requirements: exclusions, currency matching for planned relocation, or matching a defined future liability.

Large portfolios where small percentage improvements are large amounts.

And genuine access to opportunities that are both unavailable simply and supported by evidence — which is a much smaller category than the marketing suggests.

The test for any addition

Before adding anything.

What does this do that my existing holdings do not?

What is the evidence, and is it from live results or backtests?

What does it cost, in total?

How long would I have to hold it for the case to be tested?

What would make me sell it, and how likely is that?

And could I explain the whole portfolio, including this, to someone else in five minutes?

If the last answer is no, the portfolio has probably exceeded useful complexity.

The accumulation problem

How complexity arrives.

Rarely by decision — generally by accumulation, as holdings are added over years for reasons that made sense at the time and were never revisited.

Which produces portfolios of many overlapping funds with no coherent structure.

The corrective is an annual review that asks what each holding is for, and a willingness to simplify rather than only to add.

The uncomfortable conclusion

Worth stating.

A single global multi-asset fund, held for decades with automated contributions and no interference, produces an outcome that most self-managed portfolios do not beat.

It generates nothing to discuss, requires no research and provides no sense of activity.

Which are the reasons it is unpopular and are unrelated to whether it works.

General information only, not investment advice. Investments can fall in value and past performance does not indicate future returns. Consult a regulated financial adviser.