‘Don’t put all your eggs in one basket’ may be a cliche but it’s also the best investment advice you’ll ever receive.


Diversification is your first line of defence against the extreme circumstances summed up in the famous quote: ‘The market can remain irrational longer than you can remain solvent.’ by Dominique Riedl

Of course, the basket, in this case, is your portfolio and the eggs are asset classes. Bet your future prosperity on a single position and you risk coming unstuck like an investor in the Japanese stock market circa 1989.

Ultimately, nobody can guarantee how events will unfold. You don’t want to be the cautionary tale who bet the house on tech stocks in early 2000, or went to cash during the 2008 meltdown and missed the bull market starting 2009 or put everything into Bitcoin during December 2018.

‘The market can remain irrational longer than you can remain solvent.’

But it’s easy to get carried away during a bubble or a crisis, hence Harry Markowitz won the Nobel Prize in economics for stiffening investors resolve by turning ‘eggs-in-a-basket’ adages into a rigorous mathematical model.

His work showed that an investment portfolio of assets with varying expected returns and volatilities could be combined to reduce overall risk (or boost overall performance) for an investor.

Fast forward to today and diversification is the big bazooka in the armoury of every long-term investor including global pension funds and renowned US universities such as Harvard and Yale. As Markowitz said, “Diversification is the only free lunch in finance.”

Diversification works on two levels. Firstly, it works horizontally across asset classes e.g. a diversified portfolio includes equities and bonds. Secondly, diversification works vertically within asset classes e.g. your equity allocation includes many different types of firm spread across geography, sectors, size, style and so on.

Diversification across asset classes

Horizontal diversification across asset classes is the simplest and most effective way to spread your risk.

This is because equities and bonds offer positive expected returns over the long term but often respond differently to the economic conditions.

Equities typically outperform other assets during boom times but high-quality government bonds are often a safe haven during a downturn and can compensate investors when stock markets fall.

Moreover, if equities unexpectedly underperform for a decade then a broad asset allocation in bonds, property and commodities ensures you aren’t caught with a single egg in your basket.

Diversification within asset classes

Imagine buying into Amazon in 1997; with a portfolio full of Amazon shares you’d be rich now, no?

Well only if you could stand the 95% loss on your investment it took during the dotcom bust. Plus multiple double-figure drawdowns in the 20 years since.

Amazon has been a gut-wrenching ride for its investors. And who knew Amazon was going to be the big winner in 1997? Plenty of investors bought into pets.com or the many other dotcoms that sounded like the next big thing but aren’t with us today.

That’s why you shouldn’t bank everything on a single firm. Individual securities are too vulnerable to misfortune, bad management, fraud, a change in regulation that renders it a loser.

‘Individual securities are too vulnerable to misfortune, bad management, fraud, a change in regulation that renders it a loser’

These are real, idiosyncratic risks that can be diversified away when you invest broadly enough within an asset class.

The classic diversification rule-of-thumb for equities is to hold at least 30 positions. That came into fashion before funds were widespread, but now it’s easy to hold hundreds or thousands of securities through ETFs that track broad indices.

The same logic applies to diversification across countries, regions and sectors. The poster child for country risk is Japan – its stock market has still not recovered its 1989 high water mark. But every country is vulnerable.

For example, the UK stock market is highly concentrated in oil, commodity and financial companies while utterly deficient in tech firms.

‘now it’s easy to hold hundreds or thousands of securities through ETFs that track broad indices’

The UK was hit hard in 2008 when banks bore the brunt of the Global Financial Crisis while oil companies will have to cope with decarbonisation for decades to come. The answer? Diversify globally – you can’t spread your risks any further than that.

You can also easily diversify your positions in other asset classes by using ETFs. You can invest your bond allocation globally across government bondscorporate bonds and index-linked bonds.

You should also consider a range of maturities and risk ratings. In commodities, you can invest in precious metals, agricultural commodities, energy and more.

Mixing risky assets lowers risk

It’s not hard to see why a lower volatility asset like government bonds reduces the risk of an equity-dominated portfolio. But adding higher volatility assets like gold can also reduce your portfolio’s overall risk.

This can work because the correlation between gold and equities has historically been low or even negative. So it can outperform when either or even both of the more conventional asset classes underperform.

You can see how this works in the chart below. An example comparison of the five-year volatility of an MSCI World ETF with the volatility of a gold ETC makes it clear that both investments fluctuate strongly, at 18.53% and 14.69%, respectively. The combined portfolio, on the other hand, has a volatility of only 12.71% (as of 06/09/2023). The low or negative correlation contributes to risk minimization.

Comparison MSCI World ETF and Gold ETC over five years (06.09.2018 – 06.09.2023)



Item Investment
in Pounds
Final value
in Pounds
per Risk
MSCI World-ETF 5,000.00 8,163.31 63.27% 10.30% 18.53% 0.56
Gold-ETC 5,000.00 8,549.47 70.99% 11.31% 14.69% 0.77
Portfolio 10,000.00 16,712.78 67.13% 10.81% 12.71% 0.85


Source: justETF Research; as of 06/09/2023


Diversification against uncertainty

Some risks can’t be captured by the models because they are unprecedented: these are the black swan events made famous by the crisis theorist, Nassim Taleb.

It’s this uncertainty that makes diversification necessary. Do not make the classic mistake of thinking you can predict the future.

Investors down the ages have lost money by making one-way bets on the next sure thing that wasn’t.
No opportunity comes without risk so diversify, diversify, diversify.



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