Guide · 5 min read
Don't put all your eggs in one basket. That's the whole idea. Here's what it actually looks like when you're choosing investments, and why it matters far more than people realise.
Diversification means spreading your money across lots of different investments instead of betting it all on one. If you own shares in one company and it collapses, you lose everything. If you own shares in two thousand companies and one collapses, you barely notice.
That's it. The maths gets clever, the principle doesn't.
Most people underestimate how often individual investments go very wrong. Famous, well-run companies vanish — Lehman Brothers, BHS, Carillion, Wirecard. Entire sectors can underperform for a decade (UK banks after 2008). Whole countries can stagnate (Japanese shares spent more than 30 years below their 1989 peak).
You don't know in advance which company, sector or country will be the next disappointment. Diversification means you don't have to know.
Owning many companies instead of one or two. The minimum sensible number is in the hundreds, not the dozens.
A UK-only portfolio is a bet on the UK. A global portfolio works as long as the world economy as a whole keeps growing — a much safer bet over decades. The US, Europe, Japan and emerging markets all take turns leading and lagging. Owning all of them means you never miss the leader.
Shares (high growth, bumpy ride), bonds (lower growth, smoother ride), cash (no growth, no drama). Mixing them lets you tune the overall ride to what you can stomach without going to extremes.
Buy one global equity index fund. A single fund such as a FTSE All-World, MSCI World or a Vanguard LifeStrategy-style multi-asset fund gives you a stake in thousands of companies across every major market for an annual fee of around 0.1–0.25%.
That one decision handles all three levels above. It's not exciting. It's not clever. It quietly beats most professional fund managers over any decent stretch of time.
The headline
It doesn't stop markets falling. When the world economy has a bad year, almost everything falls together. Diversification means you avoid being wiped out by a single bad bet — it doesn't mean you avoid every drawdown. The thing that gets you through a bad year is staying invested, not a clever portfolio.
— Thinking 10 different UK bank shares are diversified. They aren't: they all rise and fall together.
— Holding your employer's shares plus a fund that already owns them. You're doubled up.
— Owning five "global" funds that all hold the same top 50 US companies. More funds isn't always more diversification.
— Treating crypto, gold or a single property as diversification when they're 70% of your wealth.
Diversification means spreading your money across lots of different investments, so that if one of them does badly, the others can carry the load. The classic version is owning hundreds or thousands of companies at once instead of just a handful.
Individual companies, sectors and even whole countries can underperform for years or collapse entirely. Diversification means no single bad bet can wreck your wealth. It also smooths out the ride, which makes it much easier to stay invested when markets fall.
Buy one global index fund. A single fund like a FTSE All-World or MSCI World tracker gives you a share of around 1,500–4,000 companies across dozens of countries and every major industry, for a fee of around 0.2% a year.
No. Twenty shares of one company is one bet, not twenty. Diversification is about owning many different things, not many units of the same thing.
In theory yes — once you own a global index fund, adding more funds that own the same companies just adds complexity without lowering risk. For almost everyone, the bigger danger is being under-diversified, not over.
General information, not financial advice.