What to consider before investing in small-cap indexes
Small-cap index trackers show why your choice of benchmark can make a large difference to long-term returns


The small-cap effect is more inconsistent than many investors assume. Smaller stocks have beaten larger ones over decades, but they have oscillated between long spells of outperformance and underperformance.
In recent years, they have seen a long streak of underperformance. That doesn’t mean that we should ignore small caps, but we should think about whether this is likely to persist and why.
However, before getting that far, investors who want to track small-cap indexes need to consider what they are buying. We can see this most clearly in the US, where there is a choice of competing small-cap indexes.
MoneyWeek
Subscribe to MoneyWeek today and get your first six magazine issues absolutely FREE

Sign up to Money Morning
Don't miss the latest investment and personal finances news, market analysis, plus money-saving tips with our free twice-daily newsletter
Don't miss the latest investment and personal finances news, market analysis, plus money-saving tips with our free twice-daily newsletter
Look beyond the obvious in US small-cap indexes
The best-known US small-cap index – and the one with the most assets in UK-listed exchange traded funds (ETFs) – is the Russell 2000. This covers the 2,000 smallest stocks in the Russell 3000, which is FTSE Russell’s whole-of-market US benchmark. As this implies, there is a Russell 1000 index of larger stocks, which gets little attention – all the focus at the larger end of the market is on the S&P 500 index. In turn, the S&P 500 is one of three benchmarks in its own series, alongside the S&P MidCap 400 and the S&P SmallCap 600, which are often ignored in favour of the Russell 2000.
Add all these numbers up and you can quickly see that while both the S&P 600 and Russell 2000 are viewed as small-cap proxies, they will have different market coverage. There is overlap, but some stocks will be in one and not the other.
Still, the most critical difference between the two is something less obvious. S&P requires a stock to have been profitable for four quarters before being added to the index (although not to stay in it), while FTSE Russell has no such requirement. This acts as a very crude quality filter. Some passive purists object to this – they argue an index should simply reflect the market – but the S&P 600 has beaten the Russell 2000 by around 1%-2% per year over longer time periods (although obviously not in every individual year – the Russell did a bit better in 2023).
Appeal of UK small cap indexes
We don’t have quite the same choice for the UK, where the options are mostly limited to FTSE 250 funds. There are indexes such as the FTSE SmallCap and the FTSE Fledging, as well as the FTSE Aim series (the latter is not simply about size – some Aim stocks are FTSE 250-sized, but don’t comply with the rules for a full listing and so aren’t included in the main indexes). However, trackers aren’t available for any of these.
There is one exception: the MSCI UK Small Cap, where iShares offers an ETF. In one way, this is less focused on small stocks than the FTSE 250, since it includes the bottom end of the FTSE 100, but there are other differences. It doesn’t include investment trusts – about 30% of the FTSE 250 – but it does include some of the larger Aim stocks. How much does this matter? For a long time, not much – but recently, a large gap has opened up.
This article was first published in MoneyWeek's magazine. Enjoy exclusive early access to news, opinion and analysis from our team of financial experts with a MoneyWeek subscription.
Get the latest financial news, insights and expert analysis from our award-winning MoneyWeek team, to help you understand what really matters when it comes to your finances.
Cris Sholto Heaton is an investment analyst and writer who has been contributing to MoneyWeek since 2006 and was managing editor of the magazine between 2016 and 2018. He is especially interested in international investing, believing many investors still focus too much on their home markets and that it pays to take advantage of all the opportunities the world offers. He often writes about Asian equities, international income and global asset allocation.
Cris began his career in financial services consultancy at PwC and Lane Clark & Peacock, before an abrupt change of direction into oil, gas and energy at Petroleum Economist and Platts and subsequently into investment research and writing. In addition to his articles for MoneyWeek, he also works with a number of asset managers, consultancies and financial information providers.
He holds the Chartered Financial Analyst designation and the Investment Management Certificate, as well as degrees in finance and mathematics. He has also studied acting, film-making and photography, and strongly suspects that an awareness of what makes a compelling story is just as important for understanding markets as any amount of qualifications.
-
What is the 25x retirement rule and does it work?
The 25x retirement rule has been around for decades but many experts question if it is a suitable strategy
-
When is the self-assessment tax return deadline?
If you are self-employed, rent out a property or earn income from savings or investments, you may need to complete a self-assessment tax return. We run through the deadlines you need to know about
-
Are wealthy whisky enthusiasts leaving Britain?
Collectables Wealthy whisky enthusiasts are heading to tax-friendly countries such as Dubai, where there is more disposable income to spend on collectable luxuries like rare whisky.
-
'The rise and fall of Kodak is a lesson for the tech giants'
Opinion The long decline of Kodak – a once-dominant company – shows why no business is safe from disruption, says Matthew Lynn
-
8 of the best properties for sale with kitchen gardens
The best properties for sale with kitchen gardens – from a 17th-century timber-framed hall house in Norfolk, to an Arts & Crafts house in West Sussex designed by Charles Voysey with a garden by Gertrude Jekyll
-
Why investors can no longer trust traditional statistical indicators
Opinion The statistical indicators and data investors have relied on for decades are no longer fit for purpose. It's time to move on, says Helen Thomas
-
Investors rediscover the virtue of value investing over growth
Growth investing, betting on rapidly expanding companies, has proved successful since 2008. But now the other main investment style seems to be coming back into fashion.
-
8 of the best properties for sale with shooting estates
The best properties for sale with shooting estates – from an estate in a designated Dark Sky area in Ayrshire, Scotland, to a hunting estate in Tuscany with a wild boar, mouflon, deer and hare shoot
-
What we can learn from Britain’s "Dashing Dozen" stocks
Stocks that consistently outperform the market are clearly doing something right. What can we learn from the UK's top performers and which ones are still buys?
-
The most likely outcome of the AI boom is a big fall
Opinion Like the dotcom boom of the late 1990s, AI is not paying off – despite huge investments being made in the hope of creating AI-based wealth