Do you really have a diversified portfolio?

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Why should I care about diversification?

Think of your portfolio as a football team. You wouldn't send out eleven strikers and hope for the best. They might score plenty of goals on a good day, but the moment the other side gets the ball, you're in trouble. A balanced team needs defenders, midfielders and forwards, each doing a different job.

Investing works the same way. Different types of investment behave differently. SharesA unit of ownership in a company. Companies divide their ownership into shares and investors can purchase these to become owners of a tiny part of it. They're also called 'stocks' or 'equities'., bondsA type of asset that represents a loan, usually issued by a government, company or agency that wants to raise money to fund its operations., property and cash tend to rise and fall at different times and for different reasons. When one part of your portfolio is having a rough patch, another part may be holding steady or even doing well.

That's the whole point of diversificationThe process of spreading your investment portfolio across different asset classes, such as partially in shares and partially in bonds, in order to reduce risk.. It isn't about avoiding losses altogether, because no portfolio can do that. It's about making sure one bad result doesn't knock you out of the competition. A well-spread portfolio should give you a smoother ride over time, which makes it much easier to stay invested when markets wobble. And staying invested is often half the battle.

The diversification myth

Here's the problem. Most people think diversification simply means owning several investments.

It's an easy assumption to make. If you hold 15 different shares, it feels like your eggs are in lots of baskets. But if those 15 shares are all large US technology companies, they're likely to move in much the same direction at much the same time. You don't have 15 baskets. You have one big basket with 15 eggs in it.

Research from Quilter and Boring Money shows how common this misunderstanding is. More than half of investors (54%) believe their investments are well diversified. Yet 12% of all investors say they're diversified while holding only individual shares or bonds, with no funds, no ready-made portfolios and nothing else spreading the risk for them.

True diversification asks a different question. It doesn't ask "how many things do I own?" It asks "how many different things do I own, and how differently do they behave?" That means thinking about:

Signs your portfolio may not be as diversified as you think

Concentration risk has a habit of sneaking in quietly. Here are some of the most common warning signs.

Your funds own the same things. Holding three or four different funds can look like a nicely spread portfolio. But many popular global funds have a big slice in the same handful of giant US companies. Look under the bonnet and you may find you own the same shares several times over.

You only own individual shares. Picking shares can be rewarding, but building a properly diversified portfolio this way takes a lot of holdings, a lot of research and a lot of ongoing monitoring. Most people who go it alone with shares end up more concentrated than they realise.

One theme dominates. If most of your recent purchases share a story, such as AI, clean energy or a particular market, your portfolio may be leaning heavily one way.

You're heavily invested close to home. Lots of UK investors lean towards UK companies because they're familiar. Others hold large amounts of shares in the company they work for. If your job and your investments depend on the same thing, a bad year could hit both at once.

Your money is spread across several accounts. An ISAA type of tax-free savings or investment account which allows you to put away up to £20,000 every tax year without paying taxes. There are four main types - Cash ISAs, Stocks & Shares ISAs, Junior ISAs, and Lifetime ISAs. here, a SIPPA type of pension that allows individuals to save for retirement by managing their own investments. They come with tax relief designed to incentivise you to save for retirement. there, a share-dealing account somewhere else. Each one might look sensible on its own, but nobody is looking at the whole picture. Overlaps and gaps are much harder to spot this way.

You haven't rebalanced in a while. Even a well-spread portfolio can drift. If one investment has done brilliantly, it may now make up a much bigger share of your money than you ever intended, and that means more risk riding on it.

Even the most confident investors can get diversification wrong

You might expect diversification mistakes to come mostly from nervous beginners. In practice, the research suggests confident, hands-on investors can be just as vulnerable, sometimes more so.

Boring Money's DIY Investor Persona Report, based on more than 8,400 DIY investors surveyed over four years, found that Active Traders make up around a quarter of all DIY investors. They're confident, experienced and engaged. Eight in ten (80%) hold individual shares, and more than half use more than one investment platform. That's a lot of moving parts, and a lot of scope for overlap without anyone joining the dots.

Engaged Optimisers tell a similar story. They're the youngest group, with an average age of 38 and around six years of investing experience. They're enthusiastic and committed, and 77% say they like picking lots of different types of investments. But more choice doesn't automatically mean more balance. Two-thirds (67%) hold individual shares and 43% hold crypto, both of which can add a lot of risk if they make up a big part of the portfolio.

Meanwhile, ready-made investments, which are built to do the diversifying for you, are held by only a minority in every investor group, from 16% to 35% depending on the type of investor.

None of this means confident investors are doing it wrong. Many have well-built portfolios. But confidence and diversification aren't the same thing. The more hands-on you are, the more likely you are to make lots of individual decisions, and lots of individual decisions don't always add up to a balanced whole. It's the investing version of a manager who keeps signing exciting forwards and forgets the team hasn't got a goalkeeper.

Please note Quilter advisers are unable to offer advice on Crypto.

Source: DIY persona report 2026 | Boring Money Business

How an adviser can help

Diversification is one of those things that's simple in principle and surprisingly fiddly in practice. That's where a financial adviser can add real value, whatever your level of experience. An adviser can:

Portfolio sense check

Not sure where you stand? Run through these questions. If you answer "no" or "I'm not sure" to more than a couple, it may be worth taking a closer look, or speaking to an adviser.

Diversification won't make your investments bulletproof. But it can stop one bad bounce from deciding the whole match.

Investing can help your money grow over the long term, especially when compared to holding cash. You should keep in mind that investment values can go down as well as up and it’s not guaranteed.

Diversification does not guarantee a profit or protect against loss. This article is for information only and is not financial advice.

Approver: Quilter Financial Services Ltd. October 2026.