Large-cap shares: the trade-offs of buying the obvious names
The FTSE 100 is the obvious place to start. But the comfort of owning a household name comes with trade-offs every UK beginner should understand.
There is a particular comfort that comes with owning large-cap shares. The logo is familiar. The brand sits on the supermarket shelf or in your bank app, and the share price appears on the evening news. For a lot of first-time investors, the FTSE 100 is the obvious starting point for exactly this reason. The companies in it are big, established, and visible. There is nothing wrong with that as an instinct. But that comfort comes with trade-offs worth understanding before you commit real money.
What is a large-cap share?
A large-cap share is a company with a market capitalisation in the billions of pounds. Market capitalisation is the share price multiplied by the number of shares in issue. It is the standard yardstick for measuring how big a listed company is. In the UK, the FTSE 100 is the index of the 100 largest companies on the London Stock Exchange by market cap. To be in the index, a company typically needs to be worth several billion pounds. The threshold moves as the index is rebalanced quarterly. At the top end you have giants like AstraZeneca, Shell, HSBC and Unilever, each worth well over £100 billion. At the bottom end you find companies that have slipped from a higher position or pushed up from the FTSE 250. The range is wide.
Why large-cap shares appeal to new investors
The first practical advantage of large-cap shares is liquidity. There are always plenty of buyers and sellers, which means you can get in and out without moving the price against yourself. The bid-offer spread on these shares is usually tiny, often a fraction of a penny on a share priced in pounds. On a smaller AIM-listed company, the spread might be ten or fifteen per cent of the bid price. That is a hidden cost you pay before the share has moved at all. Understanding what the bid-offer spread actually costs you is one of the most practical things a new investor can learn.
For a beginner placing modest orders, the difference between a 0.1 per cent spread and a 15 per cent spread is significant. The first is near-frictionless. The second needs a sizeable share-price rise just to break even.
The second advantage is information. These companies are followed by dozens of analysts. Every announcement is dissected, every set of results is forecast in advance, every strategy update is picked apart on the day. Shell’s break-even oil price is documented in analyst notes. The information is online within minutes of any update. That depth of free research is genuinely useful for an investor who wants to understand what they own.
The real trade-offs of large-cap investing
This is also where the trade-offs begin. Well researched does not mean well priced. When every professional investor reads the same broker notes and builds the same models, prices move quickly. Most of what is publicly known is already in the price. Bargains are rare not because they cannot exist, but because everyone is looking. Obvious mispricings tend to get arbitraged away within hours rather than months. If you want to find an under-researched gem, you are unlikely to find it among the FTSE 100.
The third trade-off is the growth ceiling. A company worth £200 billion does not double in size easily. To grow earnings by twenty per cent in a year, a small company needs to add a modest amount in absolute terms. For a company at that scale, it needs to add billions of pounds of new earnings, which is far harder to engineer. Much of the capital growth in long-run equity portfolios comes from smaller and mid-sized companies. They tend to deliver returns through moderate appreciation and dividends rather than spectacular price rises. That is fine if you understand what you are buying. It is a problem if you bought a FTSE 100 stalwart expecting it to triple.
The fourth and most important trade-off is the one most people would rather not hear. Big does not mean safe. The recent history of the British stock market is full of large-cap shares that proved far more fragile than their size suggested. Marconi collapsed in 2001 after a calamitous shift into telecoms at the top of the dot-com bubble. It had been one of the most respected industrial names in the index. Shareholders who treated it as a sleep-easy holding lost almost everything. More recently, names like Carillion, Thomas Cook and Debenhams have shown that index membership is no guarantee of survival. When one of these companies fails, the equity holders typically come last in the queue.
How to use large-cap shares in a portfolio
The implication for a first-time investor is not that large-cap shares should be avoided. They are usually the right place to start. The liquidity, the dividends and the information depth all matter when you are learning the mechanics. But the way to use them is with realistic expectations. Buy them for income, for relative stability, for the comfort of holding businesses you understand. Do not buy one expecting a tenfold return. Do not assume that because the company has been around for a century, it will still be around in another decade. The market can revalue any name when the facts change. The facts change more often than the brand on the side of the building suggests.
In practice, most balanced UK portfolios hold large-cap shares alongside some exposure to mid-caps and small-caps. They provide ballast. The smaller companies provide more growth potential, and more risk. Our guide to building a balanced portfolio covers how different asset classes work alongside each other. The single thought to take from all of this: size is a feature of an investment, not a verdict on its quality. The FTSE 100 is a good starting point, not a finished answer.
Key takeaways
- A large-cap share is a company with a market capitalisation in the billions; in the UK that means the FTSE 100.
- The main practical advantages are liquidity and a deep flow of free analyst research.
- Well researched does not mean well priced; the FTSE 100 is among the most efficiently priced markets in the world.
- Very large companies struggle to grow earnings quickly, so returns come mainly through income and moderate appreciation.
- Big does not mean safe. Marconi, Carillion and Thomas Cook were all FTSE 100 names before they failed.
- Use large-cap shares as portfolio ballast and pair them with mid and small-caps if you want growth potential.
Nothing in this article is financial advice. Tax rules change frequently. Check the current ISA allowance, CGT exemption and relevant rules on HMRC’s website or consult a qualified financial adviser for your specific situation.
Money & Markets is a guide to personal finance and investing for people who want to understand the world they live in.
Disclaimer: The value of investments can go down as well as up, and you may get back less than you invest. This article is for informational and educational purposes only and does not constitute financial advice. Always do your own research and consider seeking independent advice before making any investment decision.