The investment industry is built on a compelling but largely false premise: that skilled professionals can identify which stocks and markets will outperform, and that paying for their expertise will produce better results than simply investing in everything.

The evidence is clear and has been clear for decades. The majority of actively managed funds underperform their benchmark index after fees, over almost any meaningful time period. The minority that outperform in one period do not reliably continue outperforming in the next. Identifying which active funds will outperform in advance is, for most investors, impossible.

The solution was identified by John Bogle and others in the 1970s: instead of trying to beat the market, just own the market.

The problem with picking winners

Beating the market — achieving higher returns than a relevant market index — sounds straightforward. If some stocks go up more than others, surely a skilled analyst can identify which ones before it happens.

The problem is that the stock market is highly competitive. When you buy a share, you are buying it from someone who has decided to sell. Both of you have access to the same publicly available information. For you to be buying at a price that will prove too low, the seller must be systematically wrong. In a market with millions of participants, many of them sophisticated professionals, the opportunity to be systematically right is thin.

Academic research beginning with Eugene Fama’s work on the Efficient Market Hypothesis formalised this intuition. In its most practical form, the hypothesis says that publicly available information is already incorporated into share prices, making it very difficult to consistently earn excess returns by analysing that information.

The data confirms it. According to SPIVA (S&P Indices Versus Active) reports published twice annually, typically 60-90% of active funds underperform their benchmark index over 10-15 year periods, depending on the market. In some asset classes and some periods, virtually no active funds beat their benchmark after fees.

What an index fund is

An index fund is a fund that tracks a market index — a pre-defined list of securities meeting certain criteria. The FTSE 100 tracks the 100 largest companies listed on the London Stock Exchange. The S&P 500 tracks the 500 largest US companies. The MSCI World tracks approximately 1,500 large and mid-cap companies across 23 developed countries.

An index fund tracking the MSCI World holds small proportions of all 1,500 companies, weighted by their market capitalisation (the larger the company, the larger the proportion). When any company is added or removed from the index, the fund adjusts accordingly — automatically, without human judgement about which companies to favour.

Because there are no analysts to pay and no complex research to conduct, the costs of managing an index fund are very low. Typical annual management fees (expense ratios) for index funds and ETFs tracking major indices are 0.05–0.20%, compared to 0.75–1.5% for actively managed funds.

Why passive beats active

The arithmetic of active management is the core argument for indexing. In aggregate, all investors own the entire market. Therefore, the average investor earns the market return before costs. After costs, the average investor earns below the market return. Passive investors, by owning the whole market at very low cost, reliably earn close to the market return after costs. Active investors, on average, earn significantly less.

This is not a prediction about the future — it is an accounting identity. It must be true that active investors in aggregate underperform passive investors after costs, because active investors incur higher costs while together owning the same aggregate portfolio.

The second argument is behavioural. Active managers, by definition, make decisions about when to buy and sell. They also respond to client pressure — investors tend to withdraw money during downturns and add money during bull markets, which forces managers to sell low and buy high. Index funds, because they follow a rule rather than making decisions, avoid the behavioural errors that compound the underperformance of active management.

ETFs vs. mutual funds

Index funds come in two main wrappers: traditional mutual funds and Exchange Traded Funds (ETFs).

Traditional index funds are priced once per day at the close of the market. You buy and sell at that daily price. Minimum investment amounts vary; some funds have low minimums of £25-100.

ETFs trade on stock exchanges throughout the day, like individual shares. You can buy or sell at any point during trading hours. Because of this flexibility, there is typically a small bid-ask spread (the difference between the buying and selling price) that mutual funds do not have.

For long-term investors making regular contributions, this distinction is largely irrelevant. Both are excellent vehicles for passive investing. The choice usually comes down to which your investment platform supports and what minimum amounts are required.

Getting started

A simple, evidence-based portfolio for a long-term investor might consist of:

  • A global equity index fund (such as one tracking the MSCI World or FTSE All-World)
  • Optionally, a government bond index fund for ballast, in a proportion matching your risk profile

The global equity fund alone provides exposure to thousands of companies across dozens of countries. Combined with low costs and regular contributions, this is a portfolio that the evidence suggests will outperform the majority of actively managed alternatives over the long term.

Platforms that provide access to low-cost ETFs and index funds include Vanguard, iShares, and many online brokers. Opening an account, selecting a fund, and setting up a regular contribution can be done in an afternoon.

After that, the most important discipline is the simplest: do not react to short-term market movements. Buy, hold, contribute regularly, and let compounding do the work.