Investment fundamentals

The main asset classes

An asset class is a group of investments that share economic characteristics and tend to behave similarly. The conventional groupings are:

• Cash and equivalents. Bank deposits, money market instruments, short-term treasury bills. Low volatility, high liquidity, and vulnerable to inflation over long periods.
• Fixed income (bonds). Loans to governments or companies that pay interest and return principal at maturity. Sensitive to interest rates and to the borrower's credit quality.
• Equities (stocks). Ownership shares in companies. Historically the highest long-run expected return of the mainstream classes, with correspondingly large declines along the way.
• Real assets. Property, infrastructure and commodities. Often held for their different response to inflation.
• Alternatives. Private equity, private credit, hedge strategies and similar. Typically less liquid, more complex, more expensive, and harder to evaluate.

These labels are conveniences, not laws of nature. A high-yield bond behaves more like equity than like a treasury bond in a crisis, and a real-estate investment trust is legally equity with property economics underneath.

Risk and return

The core relationship in investing is that expected return compensates for risk borne. Investors demand more expected return to hold assets whose outcomes are less certain. Two clarifications make this idea far more useful:

Expected return is not promised return. It is the centre of a distribution of possible outcomes. Realised results scatter widely around it, and the scatter is precisely the risk being compensated. An asset with a higher expected return can and does underperform a lower-risk asset for extended periods — that possibility is why the higher expectation exists at all.

Not all risk is compensated. Markets pay you for bearing risk that cannot be diversified away. Holding a single company instead of a broad index adds risk specific to that company, and there is no reason to expect payment for it, because you could have removed it for free by diversifying. That distinction — systematic versus idiosyncratic risk — underpins most of modern portfolio construction. It is developed further in the asset allocation guide.

The kinds of risk

Compounding and time

Compounding is growth on prior growth. Its defining feature is that it is not linear: the effect is modest for a long time and then becomes dominant, which is why the variable that matters most is duration rather than rate.

The same mechanism runs in reverse. Costs, taxes and losses also compound, and they compound against the base that would otherwise have been growing. A percentage point of annual fee is not a percentage point of your return; it is a percentage point plus all the future growth that point would have produced.

Volatility and drawdown

Volatility measures how much returns fluctuate around their average, usually expressed as annualised standard deviation. It is the industry's default proxy for risk because it is easy to calculate — not because it captures everything that matters. It treats upside and downside movement identically, and it says nothing about the risk of a permanent loss.

Drawdown — the peak-to-trough decline — is often the more meaningful figure, because it describes the experience an investor has to endure. Recovering from a decline requires a larger percentage gain than the percentage lost: a 20% fall needs 25% to get back, a 50% fall needs 100%. This asymmetry is arithmetic, and it explains why avoiding catastrophic losses matters more than capturing every gain.

Cost and its drag

Returns are uncertain; costs are not. This makes cost the single most controllable input in a portfolio. The costs an investor bears include:

• Fund expense ratios — deducted continuously from fund assets, so they never appear as a line on a statement.
• Advisory or platform fees — typically a percentage of assets, sometimes a flat retainer.
• Trading costs — commissions where they still apply, plus the bid-ask spread and market impact, which are invisible but real.
• Product-level costs — sales loads, surrender charges, wrapper and rider fees in insurance-linked products.
• Tax — the largest cost for many taxable investors, and the one most affected by structure. See tax-aware investing.

The useful question is not "is this cheap?" but "what am I receiving in exchange for this cost, and could I obtain the same thing for less?" A fee that buys genuine planning and coordination may be excellent value. The same fee buying only asset allocation that could be replicated with three index funds is a different proposition.

Funds, ETFs and direct holdings

Most investors access asset classes through pooled vehicles rather than by buying securities directly.

• Mutual funds pool investor money and are priced once daily at net asset value.
• Exchange-traded funds hold a similar portfolio but trade on an exchange throughout the day. Their structure often makes them more tax-efficient in taxable accounts, though this varies.
• Index funds — available in both wrappers — aim to track a published index rather than beat it, which typically means lower turnover and lower cost.
• Actively managed funds aim to outperform a benchmark. They cost more, and the persistence of outperformance across periods is one of the most heavily studied and heavily debated questions in finance.
• Direct holdings give control over individual positions and tax lots, at the cost of concentration risk and the effort of managing them.

Behaviour

The gap between what investments return and what investors actually earn is largely behavioural. Money tends to arrive after good performance and leave after bad, which is the reverse of what the arithmetic rewards. The recurring patterns are well documented:

• Loss aversion — losses feel roughly twice as significant as equivalent gains, which biases decisions toward avoiding short-term discomfort.
• Recency bias — the recent past feels like the future, so risk appetite peaks at the top and vanishes at the bottom.
• Overconfidence — usually expressed as excessive trading, which reliably adds cost and rarely adds return.
• Anchoring — fixating on a purchase price that the market has no knowledge of.
• Herding — treating widespread agreement as evidence, when it is often the opposite.

The standard defences are structural rather than motivational: write the strategy down before it is tested, automate contributions, set a rebalancing rule in advance, and reduce how often you look. None of this requires unusual discipline — it requires removing the moments where discipline is needed.