British investors often keep most of their money close to home. This tendency to favour domestic shares over international ones is known as home bias. While investing in familiar British companies seems safe, it exposes your portfolio to unnecessary risks because the UK market is only a small piece of the global financial pie.
The Hidden Risk of Domestic Market Concentration
The UK stock market represents around 3% to 4% of global market capitalisation. When you put the majority of your cash into British equities, you miss out on the rest of the global market. This narrow focus creates a concentration problem.
The FTSE 100 is heavily weighted towards a handful of traditional sectors, with consumer staples, financials, energy and healthcare making up the bulk of the index. It lacks significant exposure to high-growth sectors like technology, which drives a massive portion of modern global economic growth.
It’s also worth remembering that around 70% of FTSE 100 revenues come from outside the UK, so the index is less of a pure bet on the British economy than it looks. Even so, without international assets, much of your financial growth is tied to older, legacy industries.
If you only own UK shares, your financial future depends on a few massive companies. Building a properly diversified portfolio across regions and asset classes is harder than it sounds, which is why many investors turn to Rathbones investment management, who build globally diversified portfolios tailored to each client’s specific needs and objectives. Spreading your capital across different countries ensures that a downturn in the UK economy won’t crush your entire portfolio.
How Global Returns Compare Over the Long Term
Historical data shows that a UK-only investment strategy has cost investors significant returns. Over the past 10 to 20 years, global stock markets have outperformed the UK market, with global indices driven by large American tech firms delivering higher annualised returns than the FTSE 100. The performance gap widens over longer horizons, as international markets capitalised on digital expansion while the UK market grew at a slower pace.
An investor who put all their money into a FTSE 100 tracker 20 years ago would likely have less wealth today than someone who chose a globally diversified index fund, even after reinvesting UK dividends. Since 2000, the FTSE 100 has returned roughly 4% a year with dividends reinvested, compared with around 5.6% for the MSCI World. That said, the UK market has had a stronger run recently, with the FTSE 100 climbing roughly 20% in 2025 and hitting an all-time high in early 2026. The long-term gap still favours global diversification, but the picture isn’t one-way traffic.
By spreading assets across the US, Europe and emerging markets, you capture growth from the world’s most innovative businesses instead of restricting your wealth to the UK’s slower economic trajectory. Geographic spread can also reduce long-term volatility.
When Home Bias Makes Financial Sense
Despite the benefits of international diversification, keeping some money in UK shares is completely reasonable. Investors often prefer domestic stocks because they want to avoid currency risk. When you invest overseas, changes in exchange rates can eat into your returns. If the pound strengthens against the US dollar, your American investments become worth less in pounds, even if the share prices went up.
Another reason Brits stick to domestic equities is the attractive dividend yield. UK companies have a long tradition of paying out high dividends to shareholders, which is excellent for investors who need a regular income stream.
Familiarity also plays a big part, as it’s easier to understand the business model of a high street bank or a familiar utility company than a tech firm based in Asia. A modest home bias can stabilise a portfolio, but it should be a deliberate choice instead of an accidental concentration that leaves you exposed.
How Much of Your Portfolio Should Be in UK Shares?
A successful investment plan balances local stability with international growth. Relying solely on the UK market means missing out on global innovation and exposing your savings to a concentrated group of domestic sectors. You can protect your wealth against local economic shocks by adding international assets that perform well when the UK struggles.
Review your portfolio to see how much money is tied up in British equities. If your domestic exposure is well above the UK’s small share of global markets, it might be time to rebalance. Spreading your investments across different regions helps you build a more secure financial future and gives you exposure to growth wherever it happens.
The value of your investments and the income from them may go down as well as up, and you could get back less than you invested. Past performance should not be seen as an indication of future performance.
