An index fund holds the companies in an index, in roughly the same proportions. If the index has 500 companies, the fund holds about 500 companies. Buying a single stock is the opposite: all your money depends on one company's share price, its results and its luck. Both can build wealth, and both can lose money, but they ask very different things of the investor.
This guide compares the two honestly. It covers risk, cost, the time and skill each one needs, and the question most people should ask before they choose: what kind of investor am I, and what do I want to spend my attention on?
What an index fund does
An index fund is a fund that holds the shares of an index in the same weights as the index. Its aim is to match the index's return, minus its own costs, rather than to beat it. It does not need a manager to pick winners, because the choice of companies follows the index's own rules.
An index fund gives you broad exposure in one purchase. A single fund on a broad index can hold hundreds of companies across several sectors, so the failure of one company has a small effect on the whole.
Index funds are not the same everywhere. Some track large indexes, some track sectors or countries, some use different weighting rules. Read the fund's description and its index before you buy.
What picking single stocks means
Picking single stocks means choosing which companies to own and in what amounts. The return depends on those choices. If you pick ten companies and one falls by half, that is a large part of the portfolio. If you pick one company that goes to zero, the whole investment is gone.
The upside is that a well-chosen company can do far better than the index. The downside is that a poorly chosen one can do far worse. Single-stock investing needs you to research the company, judge its prospects, know when to sell and cope with the swings along the way.
The difference in risk
A single stock carries company-specific risk, which means the risk that something goes wrong at that company: a bad result, a fraud, a lost contract, a change of management. Company-specific risk can be reduced by holding many companies, and an index fund holds many.
Both approaches still carry market risk, which is the risk that the whole market falls. An index fund cannot avoid that, and neither can a portfolio of ten stocks. Diversification removes the company risk, not the market risk.
A worked example makes the difference concrete. Suppose a market falls 20 percent over a year.
| Holding | Result in a market fall of 20% |
|---|---|
| Index fund (500 companies) | Around −20%, plus costs |
| Ten stocks, all in line with the market | Around −20% |
| One stock that falls 60% on a bad year | −60% |
| One stock that rises 30% in the same year | +30% |
The single-stock outcome spreads widely around the market's result. That spread is the risk and the opportunity at the same time.
The difference in cost
An index fund charges an annual fee, usually a small percentage of the amount invested. Trading costs are low, because the fund trades only when the index changes. A single-stock portfolio pays brokerage and spread on every trade, and it can pay more if the investor trades often.
Fees compound against you in the same way returns compound for you. A 1 percent annual difference in fees can take a noticeable share of long-term growth. Check the total costs of any fund, including the expense ratio and any trading costs inside it, and compare them with what you would pay to hold and trade shares yourself. The guide on fees and expense ratios goes through the arithmetic.
The difference in time and skill
An index fund needs very little time. You choose the fund, set a regular amount to invest, and review the position occasionally. The skill is in the choice of index and the discipline to keep investing through falls.
Single stocks need time. You must read the company's accounts, follow its news, understand its industry, and decide when to sell. The skill is in judging businesses and in controlling your own behaviour, which is often the harder part. Many investors who pick stocks underperform the index, not because they lack information, but because they trade too much and sell at the wrong moments.
What the evidence says
Over long periods, a majority of professional managers who pick stocks have trailed their benchmark index after costs. This does not mean no one can beat the market, and some investors do. It means that doing it reliably is hard, and that the average outcome after costs is usually close to the index or slightly below it.
For most people, that makes a broad index fund a reasonable core holding, and single stocks a smaller, more deliberate part of the plan, if they are held at all. Some investors use both: an index fund for the core and a small number of stocks they have researched for the rest.
Who each one suits
An index fund suits someone who wants steady, broad market exposure with low cost and low effort, and who can accept that they will never beat the market by much. It also suits someone who does not want to spend hours on company research.
Single stocks suit someone who enjoys researching businesses, who can tolerate large swings, who has a clear view of why a company is undervalued, and who has written down a plan for when to buy and sell. They also suit someone who has enough money outside the stock to take a total loss without damage.
Neither is right for everyone. The honest question is which one you will stick with through a fall of 30 percent.
The cost of getting the choice wrong
The costliest mistake is not picking the wrong fund or the wrong stock. It is switching between the two at the wrong moment. An investor who buys single stocks after a long rise, sells them in a fall, and moves into an index fund at the bottom has paid the spread, the commission and the tax twice, and missed the recovery. Decide the approach and the rules for changing it before the market moves, not during it.
Checklist before you choose
- Write down why you are investing, and over what period.
- Decide how much time you will spend on research each week.
- Check how you behaved in your last market fall, if you have had one.
- Compare the total annual cost of any fund with the cost of your trading.
- Decide the size of any single-stock position as a share of your total savings, and stick to it.
- Choose a plan for buying and selling before you buy anything.
Key takeaways
An index fund holds a broad basket of companies at low cost and needs little time, so it spreads company risk and tracks the market. Single stocks offer the chance to do better or worse than the market, and they need research, discipline and tolerance for large swings. Market risk remains in both. Most people are better served by a broad, low-cost index fund as a core holding, and any single stock should be a small, deliberate choice made with a written plan.
This guide is for general information, not financial advice. See the disclaimer.